diff --git a/src/poetry/repositories/http_repository.py b/src/poetry/repositories/http_repository.py
index 0af90e4230b..56437a590a6 100644
--- a/src/poetry/repositories/http_repository.py
+++ b/src/poetry/repositories/http_repository.py
@@ -26,6 +26,7 @@
 from poetry.repositories.exceptions import PackageNotFoundError
 from poetry.repositories.exceptions import RepositoryError
 from poetry.repositories.link_sources.html import HTMLPage
+from poetry.repositories.link_sources.json import SimpleJsonPage
 from poetry.utils.authenticator import Authenticator
 from poetry.utils.constants import REQUESTS_TIMEOUT
 from poetry.utils.helpers import HTTPRangeRequestSupportedError
@@ -417,11 +418,13 @@ def calculate_sha256(self, link: Link) -> str | None:
                 return f"{required_hash.name}:{required_hash.hexdigest()}"
         return None
 
-    def _get_response(self, endpoint: str) -> requests.Response | None:
+    def _get_response(
+        self, endpoint: str, *, headers: dict[str, str] | None = None
+    ) -> requests.Response | None:
         url = self._url + endpoint
         try:
             response: requests.Response = self.session.get(
-                url, raise_for_status=False, timeout=REQUESTS_TIMEOUT
+                url, raise_for_status=False, timeout=REQUESTS_TIMEOUT, headers=headers
             )
             if response.status_code in (401, 403):
                 self._log(
@@ -442,8 +445,25 @@ def _get_response(self, endpoint: str) -> requests.Response | None:
             )
         return response
 
+    def _get_prefer_json_header(self) -> dict[str, str]:
+        # Prefer json, but accept anything for backwards compatibility.
+        # Although the more specific value should be preferred to the less specific one
+        # according to https://developer.mozilla.org/en-US/docs/Glossary/Quality_values,
+        # we add a quality value because some servers still prefer html without one.
+        return {"Accept": "application/vnd.pypi.simple.v1+json, */*;q=0.1"}
+
+    def _is_json_response(self, response: requests.Response) -> bool:
+        return (
+            response.headers.get("Content-Type", "").split(";")[0].strip()
+            == "application/vnd.pypi.simple.v1+json"
+        )
+
     def _get_page(self, name: NormalizedName) -> LinkSource:
-        response = self._get_response(f"/{name}/")
+        response = self._get_response(
+            f"/{name}/", headers=self._get_prefer_json_header()
+        )
         if not response:
             raise PackageNotFoundError(f"Package [{name}] not found.")
+        if self._is_json_response(response):
+            return SimpleJsonPage(response.url, response.json())
         return HTMLPage(response.url, response.text)
diff --git a/src/poetry/repositories/legacy_repository.py b/src/poetry/repositories/legacy_repository.py
index f3f83bbfc01..04f82d0aa04 100644
--- a/src/poetry/repositories/legacy_repository.py
+++ b/src/poetry/repositories/legacy_repository.py
@@ -12,8 +12,9 @@
 from poetry.inspection.info import PackageInfo
 from poetry.repositories.exceptions import PackageNotFoundError
 from poetry.repositories.http_repository import HTTPRepository
-from poetry.repositories.link_sources.html import HTMLPage
-from poetry.repositories.link_sources.html import SimpleRepositoryRootPage
+from poetry.repositories.link_sources.base import SimpleRepositoryRootPage
+from poetry.repositories.link_sources.html import SimpleRepositoryHTMLRootPage
+from poetry.repositories.link_sources.json import SimpleRepositoryJsonRootPage
 
 
 if TYPE_CHECKING:
@@ -130,21 +131,21 @@ def _get_release_info(
             ),
         )
 
-    def _get_page(self, name: NormalizedName) -> HTMLPage:
-        if not (response := self._get_response(f"/{name}/")):
-            raise PackageNotFoundError(f"Package [{name}] not found.")
-        return HTMLPage(response.url, response.text)
-
     @cached_property
     def root_page(self) -> SimpleRepositoryRootPage:
-        if not (response := self._get_response("/")):
+        if not (
+            response := self._get_response("/", headers=self._get_prefer_json_header())
+        ):
             self._log(
                 f"Unable to retrieve package listing from package source {self.name}",
                 level="error",
             )
             return SimpleRepositoryRootPage()
 
-        return SimpleRepositoryRootPage(response.text)
+        if self._is_json_response(response):
+            return SimpleRepositoryJsonRootPage(response.json())
+
+        return SimpleRepositoryHTMLRootPage(response.text)
 
     def search(self, query: str | list[str]) -> list[Package]:
         results: list[Package] = []
diff --git a/src/poetry/repositories/link_sources/base.py b/src/poetry/repositories/link_sources/base.py
index 10ec64f056c..65c1c2c7dd7 100644
--- a/src/poetry/repositories/link_sources/base.py
+++ b/src/poetry/repositories/link_sources/base.py
@@ -124,3 +124,24 @@ def yanked(self, name: NormalizedName, version: Version) -> str | bool:
     @cached_property
     def _link_cache(self) -> LinkCache:
         raise NotImplementedError()
+
+
+class SimpleRepositoryRootPage:
+    """
+    This class represents the parsed content of a "simple" repository's root page.
+    """
+
+    def search(self, query: str | list[str]) -> list[str]:
+        results: list[str] = []
+        tokens = query if isinstance(query, list) else [query]
+
+        for name in self.package_names:
+            if any(token in name for token in tokens):
+                results.append(name)
+
+        return results
+
+    @cached_property
+    def package_names(self) -> list[str]:
+        # should be overridden in subclasses
+        return []
diff --git a/src/poetry/repositories/link_sources/html.py b/src/poetry/repositories/link_sources/html.py
index ef13a876395..83adf4944da 100644
--- a/src/poetry/repositories/link_sources/html.py
+++ b/src/poetry/repositories/link_sources/html.py
@@ -10,6 +10,7 @@
 from poetry.core.packages.utils.link import Link
 
 from poetry.repositories.link_sources.base import LinkSource
+from poetry.repositories.link_sources.base import SimpleRepositoryRootPage
 from poetry.repositories.parsers.html_page_parser import HTMLPageParser
 
 
@@ -68,10 +69,11 @@ def _link_cache(self) -> LinkCache:
         return links
 
 
-class SimpleRepositoryRootPage:
+class SimpleRepositoryHTMLRootPage(SimpleRepositoryRootPage):
     """
-    This class represents the parsed content of a "simple" repository's root page. This follows the
-    specification laid out in PEP 503.
+    This class represents the parsed content of the HTML version
+    of a "simple" repository's root page.
+    This follows the specification laid out in PEP 503.
 
     See: https://peps.python.org/pep-0503/
     """
@@ -81,17 +83,6 @@ def __init__(self, content: str | None = None) -> None:
         parser.feed(content or "")
         self._parsed = parser.anchors
 
-    def search(self, query: str | list[str]) -> list[str]:
-        results: list[str] = []
-        tokens = query if isinstance(query, list) else [query]
-
-        for anchor in self._parsed:
-            href = anchor.get("href")
-            if href and any(token in href for token in tokens):
-                results.append(href.rstrip("/"))
-
-        return results
-
     @cached_property
     def package_names(self) -> list[str]:
         results: list[str] = []
diff --git a/src/poetry/repositories/link_sources/json.py b/src/poetry/repositories/link_sources/json.py
index f33a679ab28..6311453cfb5 100644
--- a/src/poetry/repositories/link_sources/json.py
+++ b/src/poetry/repositories/link_sources/json.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import urllib.parse
+
 from collections import defaultdict
 from functools import cached_property
 from typing import TYPE_CHECKING
@@ -8,6 +10,7 @@
 from poetry.core.packages.utils.link import Link
 
 from poetry.repositories.link_sources.base import LinkSource
+from poetry.repositories.link_sources.base import SimpleRepositoryRootPage
 
 
 if TYPE_CHECKING:
@@ -25,8 +28,9 @@ def __init__(self, url: str, content: dict[str, Any]) -> None:
     def _link_cache(self) -> LinkCache:
         links: LinkCache = defaultdict(lambda: defaultdict(list))
         for file in self.content["files"]:
-            url = file["url"]
+            url = self.clean_link(urllib.parse.urljoin(self._url, file["url"]))
             requires_python = file.get("requires-python")
+            hashes = file.get("hashes", {})
             yanked = file.get("yanked", False)
 
             # see https://peps.python.org/pep-0714/#clients
@@ -42,7 +46,11 @@ def _link_cache(self) -> LinkCache:
                     break
 
             link = Link(
-                url, requires_python=requires_python, yanked=yanked, metadata=metadata
+                url,
+                requires_python=requires_python,
+                hashes=hashes,
+                yanked=yanked,
+                metadata=metadata,
             )
 
             if link.ext not in self.SUPPORTED_FORMATS:
@@ -53,3 +61,26 @@ def _link_cache(self) -> LinkCache:
                 links[pkg.name][pkg.version].append(link)
 
         return links
+
+
+class SimpleRepositoryJsonRootPage(SimpleRepositoryRootPage):
+    """
+    This class represents the parsed content of the JSON version
+    of a "simple" repository's root page.
+    This follows the specification laid out in PEP 691.
+
+    See: https://peps.python.org/pep-0691/
+    """
+
+    def __init__(self, content: dict[str, Any]) -> None:
+        self._content = content
+
+    @cached_property
+    def package_names(self) -> list[str]:
+        results: list[str] = []
+
+        for project in self._content.get("projects", []):
+            if name := project.get("name"):
+                results.append(name)
+
+        return results
diff --git a/tests/console/commands/test_search.py b/tests/console/commands/test_search.py
index 1696d15fec6..5e52817e00b 100644
--- a/tests/console/commands/test_search.py
+++ b/tests/console/commands/test_search.py
@@ -113,9 +113,10 @@ def test_search_only_legacy_repository(
     tester.execute("ipython")
 
     expected = """\
- Package Version Source Description
- ipython 5.7.0   legacy
- ipython 7.5.0   legacy
+ Package Version  Source Description
+ ipython 4.1.0rc1 legacy
+ ipython 5.7.0    legacy
+ ipython 7.5.0    legacy
 """
 
     output = clean_output(tester.io.fetch_output())
@@ -133,11 +134,12 @@ def test_search_multiple_queries(
     tester.execute("ipython isort")
 
     expected = """\
- Package        Version Source Description
- ipython        5.7.0   legacy
- ipython        7.5.0   legacy
- isort          4.3.4   legacy
- isort-metadata 4.3.4   legacy
+ Package        Version  Source Description
+ ipython        4.1.0rc1 legacy
+ ipython        5.7.0    legacy
+ ipython        7.5.0    legacy
+ isort          4.3.4    legacy
+ isort-metadata 4.3.4    legacy
 """
 
     output = clean_output(tester.io.fetch_output())
diff --git a/tests/installation/conftest.py b/tests/installation/conftest.py
index 316a2756d74..c15e3cb5466 100644
--- a/tests/installation/conftest.py
+++ b/tests/installation/conftest.py
@@ -21,7 +21,7 @@ def env() -> MockEnv:
 
 
 @pytest.fixture()
-def pool(legacy_repository: LegacyRepository) -> RepositoryPool:
+def pool(legacy_repository_html: LegacyRepository) -> RepositoryPool:
     pool = RepositoryPool()
 
     pool.add_repository(PyPiRepository(disable_cache=True))
diff --git a/tests/puzzle/test_solver.py b/tests/puzzle/test_solver.py
index 961ccfe733a..eb61f28706c 100644
--- a/tests/puzzle/test_solver.py
+++ b/tests/puzzle/test_solver.py
@@ -56,6 +56,16 @@
 )
 
 
+@pytest.fixture
+def legacy_repository(legacy_repository_html: LegacyRepository) -> LegacyRepository:
+    """
+    Override fixture to only test with the html version of the legacy repository
+    because the json version has the same packages as the PyPI repository and thus
+    cause different results in the tests that rely on differences.
+    """
+    return legacy_repository_html
+
+
 def set_package_python_versions(provider: Provider, python_versions: str) -> None:
     provider._package.python_versions = python_versions
     provider._package_python_constraint = provider._package.python_constraint
diff --git a/tests/repositories/fixtures/legacy.py b/tests/repositories/fixtures/legacy.py
index 1dc1fb758b3..f35a0eabad9 100644
--- a/tests/repositories/fixtures/legacy.py
+++ b/tests/repositories/fixtures/legacy.py
@@ -1,9 +1,11 @@
 from __future__ import annotations
 
+import json
 import re
 
 from pathlib import Path
 from typing import TYPE_CHECKING
+from typing import Any
 from urllib.parse import urlparse
 
 import pytest
@@ -13,14 +15,16 @@
 
 from poetry.repositories.legacy_repository import LegacyRepository
 from tests.helpers import FIXTURE_PATH_REPOSITORIES_LEGACY
+from tests.helpers import FIXTURE_PATH_REPOSITORIES_PYPI
 
 
 if TYPE_CHECKING:
     from packaging.utils import NormalizedName
+    from pytest import FixtureRequest
     from pytest_mock import MockerFixture
     from requests import PreparedRequest
 
-    from poetry.repositories.link_sources.html import HTMLPage
+    from poetry.repositories.link_sources.base import LinkSource
     from tests.types import HttpRequestCallback
     from tests.types import HttpResponse
     from tests.types import NormalizedNameTransformer
@@ -36,6 +40,14 @@ def legacy_repository_directory() -> Path:
     return FIXTURE_PATH_REPOSITORIES_LEGACY
 
 
+@pytest.fixture
+def legacy_package_json_locations() -> list[Path]:
+    return [
+        FIXTURE_PATH_REPOSITORIES_LEGACY / "json",
+        FIXTURE_PATH_REPOSITORIES_PYPI / "json",
+    ]
+
+
 @pytest.fixture
 def legacy_repository_package_names(legacy_repository_directory: Path) -> set[str]:
     return {
@@ -65,6 +77,14 @@ def legacy_repository_index_html(
     """
 
 
+@pytest.fixture
+def legacy_repository_index_json(
+    legacy_repository_directory: Path, legacy_repository_package_names: set[str]
+) -> dict[str, Any]:
+    names = [{"name": name} for name in legacy_repository_package_names]
+    return {"meta": {"api-version": "1.4"}, "projects": names}
+
+
 @pytest.fixture
 def legacy_repository_url() -> str:
     return "https://legacy.foo.bar"
@@ -91,7 +111,32 @@ def html_callback(request: PreparedRequest) -> HttpResponse:
 
 
 @pytest.fixture
-def legacy_repository(
+def legacy_repository_json_callback(
+    legacy_package_json_locations: list[Path],
+    legacy_repository_index_json: dict[str, Any],
+) -> HttpRequestCallback:
+    def json_callback(request: PreparedRequest) -> HttpResponse:
+        assert request.url
+        headers = {"Content-Type": "application/vnd.pypi.simple.v1+json"}
+        if name := Path(urlparse(request.url).path).name:
+            fixture = Path()
+            for location in legacy_package_json_locations:
+                fixture = location / f"{name}.json"
+                if fixture.exists():
+                    break
+
+            if not fixture.exists():
+                return 404, {}, b"Not Found"
+
+            return 200, headers, fixture.read_bytes()
+
+        return 200, headers, json.dumps(legacy_repository_index_json).encode("utf-8")
+
+    return json_callback
+
+
+@pytest.fixture
+def legacy_repository_html(
     http: responses.RequestsMock,
     legacy_repository_url: str,
     legacy_repository_html_callback: HttpRequestCallback,
@@ -106,9 +151,30 @@ def legacy_repository(
     return LegacyRepository("legacy", legacy_repository_url, disable_cache=True)
 
 
+@pytest.fixture
+def legacy_repository_json(
+    http: responses.RequestsMock,
+    legacy_repository_url: str,
+    legacy_repository_json_callback: HttpRequestCallback,
+    mock_files_python_hosted: None,
+) -> LegacyRepository:
+    http.add_callback(
+        responses.GET,
+        re.compile(r"^https://legacy\.(.*)+/?(.*)?$"),
+        callback=legacy_repository_json_callback,
+    )
+
+    return LegacyRepository("legacy", legacy_repository_url, disable_cache=True)
+
+
+@pytest.fixture(params=["legacy_repository_html", "legacy_repository_json"])
+def legacy_repository(request: FixtureRequest) -> LegacyRepository:
+    return request.getfixturevalue(request.param)  # type: ignore[no-any-return]
+
+
 @pytest.fixture
 def specialized_legacy_repository_mocker(
-    legacy_repository: LegacyRepository,
+    legacy_repository_html: LegacyRepository,
     legacy_repository_url: str,
     mocker: MockerFixture,
 ) -> SpecializedLegacyRepositoryMocker:
@@ -127,7 +193,7 @@ def mock(
         )
         original_get_page = specialized_repository._get_page
 
-        def _mocked_get_page(name: NormalizedName) -> HTMLPage:
+        def _mocked_get_page(name: NormalizedName) -> LinkSource:
             return original_get_page(
                 canonicalize_name(f"{name}{transformer_or_suffix}")
                 if isinstance(transformer_or_suffix, str)
diff --git a/tests/repositories/fixtures/legacy/black.html b/tests/repositories/fixtures/legacy/black.html
index 092dea09c36..8157a6a5794 100644
--- a/tests/repositories/fixtures/legacy/black.html
+++ b/tests/repositories/fixtures/legacy/black.html
@@ -5,7 +5,9 @@
 <body>
     <h1>Links for black</h1>
     <a href="https://files.pythonhosted.org/packages/fd/bb/ad34bbc93d1bea3de086d7c59e528d4a503ac8fe318bd1fa48605584c3d2/black-19.10b0-py36-none-any.whl#sha256=13001c5b7dbc81137164b43137320a1785e95ce84e4db849279786877ac6d7f6" data-requires-python=">=3.6">black-19.10b0-py36-none-any.whl</a>
+    <a href="https://files.pythonhosted.org/packages/b0/dc/ecd83b973fb7b82c34d828aad621a6e5865764d52375b8ac1d7a45e23c8d/black-19.10b0.tar.gz#sha256=c2edb73a08e9e0e6f65a0e6af18b059b8b1cdd5bef997d7a0b181df93dc81539" data-requires-python="&gt;=3.6" >black-19.10b0.tar.gz</a>
     <a href="https://files.pythonhosted.org/packages/3d/ad/1cf514e7f9ee4c3d8df7c839d7977f7605ad76557f3fca741ec67f76dba6/black-21.11b0-py3-none-any.whl#sha256=38f6ad54069912caf2fa2d4f25d0c5dedef4b2338a0cb545dbe2fdf54a6a8891" data-requires-python=">=3.6.2" data-yanked="Broken regex dependency. Use 21.11b1 instead.">black-21.11b0-py3-none-any.whl</a>
+    <a href="https://files.pythonhosted.org/packages/2f/db/03e8cef689ab0ff857576ee2ee288d1ff2110ef7f3a77cac62e61f18acaf/black-21.11b0.tar.gz#sha256=83f3852301c8dcb229e9c444dd79f573c8d31c7c2dad9bbaaa94c808630e32aa" data-requires-python="&gt;=3.6.2" data-yanked="Broken regex dependency. Use 21.11b1 instead." >black-21.11b0.tar.gz</a>
     </body>
 </html>
 <!--SERIAL 6044498-->
diff --git a/tests/repositories/fixtures/legacy/ipython.html b/tests/repositories/fixtures/legacy/ipython.html
index 555711f6ebb..54903e21059 100644
--- a/tests/repositories/fixtures/legacy/ipython.html
+++ b/tests/repositories/fixtures/legacy/ipython.html
@@ -5,6 +5,8 @@
   </head>
   <body>
     <h1>Links for ipython</h1>
+    <a href="https://files.pythonhosted.org/packages/ac/02/04a5d372b4e64f9c97b2846646aec1ce4532885005aa4ba51eb20b80e17f/ipython-4.1.0rc1-py2.py3-none-any.whl#md5=2aff56d8e78341f64663bcbc81366376" data-requires-python="&gt;=3.5">ipython-4.1.0rc1-py2.py3-none-any.whl</a><br/>
+    <a href="https://files.pythonhosted.org/packages/a0/de/f71f0c8b8a26ef28cc968fbf1859729ad3e68146cd2eb4a759e9c88da218/ipython-4.1.0rc1.tar.gz#sha256=efa3a5a676648cb18e2a2d3cd6353f3c83f0f704df8eb0eb6ae7d0dcbf187ea1" data-requires-python="&gt;=3.5">ipython-4.1.0rc1.tar.gz</a><br/>
     <a href="https://files.pythonhosted.org/packages/52/19/aadde98d6bde1667d0bf431fb2d22451f880aaa373e0a241c7e7cb5815a0/ipython-5.7.0-py2-none-any.whl#md5=20da5e0b1f79dccb37f033a885d798d7">ipython-5.7.0-py2-none-any.whl</a><br/>
     <a href="https://files.pythonhosted.org/packages/c7/b6/03e0b5b0972e6161d16c4cec8d41a20372bd0634f8cb4cc0c984b8a91db6/ipython-5.7.0-py3-none-any.whl#sha256=4292c026552a77b2edc0543941516eddd6fe1a4b681a76ac40b3f585d2fca76f">ipython-5.7.0-py3-none-any.whl</a><br/>
     <a href="https://files.pythonhosted.org/packages/3c/fd/559fead731a29eaa55cc235c8029807b2520976a937c30e9ee603f3bb566/ipython-5.7.0.tar.gz#sha256=4e7fb265e0264498bd0d62c6261936a658bf3d38beb8a7b10cd2c6327c62ac2a">ipython-5.7.0.tar.gz</a><br/>
diff --git a/tests/repositories/fixtures/legacy/json/_readme b/tests/repositories/fixtures/legacy/json/_readme
new file mode 100644
index 00000000000..6ae9145252d
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/_readme
@@ -0,0 +1 @@
+Files from tests/repositories/fixtures/pypi.org/json are used as fallback!
diff --git a/tests/repositories/fixtures/legacy/json/absolute.json b/tests/repositories/fixtures/legacy/json/absolute.json
new file mode 100644
index 00000000000..c9597d6b356
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/absolute.json
@@ -0,0 +1,36 @@
+{
+  "alternate-locations": [],
+  "files": [
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry-0.1.0-py3-none-any.whl",
+      "hashes": {
+        "sha256": "1d85132efab8ead3c6f69202843da40a03823992091c29f8d65a31af68940163"
+      },
+      "requires-python": ">=3.6.0",
+      "url": "https://files.pythonhosted.org/packages/e9/df/0ab4afa9c5d9e6b690c5c27c9f50330b98a7ecfe1185ce2dc1b19188b064/poetry-0.1.0-py3-none-any.whl"
+    },
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry-0.1.0.tar.gz",
+      "hashes": {
+        "sha256": "db33179244321b0b86c6c3645225ff2062ed3495ca16d0d64b3a5df804a82273"
+      },
+      "requires-python": ">=3.6.0",
+      "url": "https://files.pythonhosted.org/packages/d5/c5/4efe096ce56505435ccbe8aeefcd5c8c3bb0da211ef8fe58934d087daef2/poetry-0.1.0.tar.gz"
+    }
+  ],
+  "meta": {
+    "_last-serial": 0,
+    "api-version": "1.0"
+  },
+  "name": "poetry",
+  "project-status": {
+    "status": "active"
+  },
+  "versions": [
+    "0.1.0"
+  ]
+}
diff --git a/tests/repositories/fixtures/legacy/json/demo.json b/tests/repositories/fixtures/legacy/json/demo.json
new file mode 100644
index 00000000000..656e919fb86
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/demo.json
@@ -0,0 +1,22 @@
+{
+  "alternate-locations": [],
+  "files": [
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "demo-0.1.0.tar.gz",
+      "url": "https://files.pythonhosted.org/distributions/demo-0.1.0.tar.gz"
+    }
+  ],
+  "meta": {
+    "_last-serial": 0,
+    "api-version": "1.0"
+  },
+  "name": "demo",
+  "project-status": {
+    "status": "active"
+  },
+  "versions": [
+    "0.1.0"
+  ]
+}
diff --git a/tests/repositories/fixtures/legacy/json/invalid-version.json b/tests/repositories/fixtures/legacy/json/invalid-version.json
new file mode 100644
index 00000000000..dd6b906cc43
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/invalid-version.json
@@ -0,0 +1,37 @@
+{
+  "alternate-locations": [],
+  "files": [
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry-21.07.28.5ffb65e2ff8067c732e2b178d03b707c7fb27855-py3-none-any.whl",
+      "hashes": {
+        "sha256": "1d85132efab8ead3c6f69202843da40a03823992091c29f8d65a31af68940163"
+      },
+      "requires-python": ">=3.6.0",
+      "url": "poetry-21.07.28.5ffb65e2ff8067c732e2b178d03b707c7fb27855-py3-none-any.whl"
+    },
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry-0.1.0-py3-none-any.whl",
+      "hashes": {
+        "sha256": "1d85132efab8ead3c6f69202843da40a03823992091c29f8d65a31af68940163"
+      },
+      "requires-python": ">=3.6.0",
+      "url": "poetry-0.1.0-py3-none-any.whl"
+    }
+  ],
+  "meta": {
+    "_last-serial": 0,
+    "api-version": "1.0"
+  },
+  "name": "poetry",
+  "project-status": {
+    "status": "active"
+  },
+  "versions": [
+    "0.1.0",
+    "21.07.28.5ffb65e2ff8067c732e2b178d03b707c7fb27855"
+  ]
+}
diff --git a/tests/repositories/fixtures/legacy/json/isort-metadata.json b/tests/repositories/fixtures/legacy/json/isort-metadata.json
new file mode 100644
index 00000000000..76ef60a1a34
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/isort-metadata.json
@@ -0,0 +1,19 @@
+{
+  "name": "isort-metadata",
+  "files": [
+    {
+      "filename": "isort-metadata-4.3.4-py3-none-any.whl",
+      "url": "https://files.pythonhosted.org/packages/1f/2c/non-existent/isort-metadata-4.3.4-py3-none-any.whl",
+      "dist-info-metadata": {
+        "sha256": "e360bf0ed8a06390513d50dd5b7e9d635c789853a93b84163f9de4ae0647580c"
+      },
+      "hashes": {
+        "sha256": "1153601da39a25b14ddc54955dbbacbb6b2d19135386699e2ad58517953b34af"
+      }
+    }
+  ],
+  "meta": {
+    "api-version": "1.0",
+    "_last-serial": 3575149
+  }
+}
diff --git a/tests/repositories/fixtures/legacy/json/jupyter.json b/tests/repositories/fixtures/legacy/json/jupyter.json
new file mode 100644
index 00000000000..12b32e5c3d4
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/jupyter.json
@@ -0,0 +1,22 @@
+{
+  "alternate-locations": [],
+  "files": [
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "jupyter-1.0.0.tar.gz",
+      "url": "https://files.pythonhosted.org/packages/c9/a9/371d0b8fe37dd231cf4b2cff0a9f0f25e98f3a73c3771742444be27f2944/jupyter-1.0.0.tar.gz"
+    }
+  ],
+  "meta": {
+    "_last-serial": 0,
+    "api-version": "1.0"
+  },
+  "name": "jupyter",
+  "project-status": {
+    "status": "active"
+  },
+  "versions": [
+    "1.0.0"
+  ]
+}
diff --git a/tests/repositories/fixtures/legacy/json/poetry-test-py2-py3-metadata-merge.json b/tests/repositories/fixtures/legacy/json/poetry-test-py2-py3-metadata-merge.json
new file mode 100644
index 00000000000..ce837f6addd
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/poetry-test-py2-py3-metadata-merge.json
@@ -0,0 +1,28 @@
+{
+  "alternate-locations": [],
+  "files": [
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry_test_py2_py3_metadata_merge-0.1.0-py2-none-any.whl",
+      "url": "https://files.pythonhosted.org/packages/52/19/poetry_test_py2_py3_metadata_merge-0.1.0-py2-none-any.whl"
+    },
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry_test_py2_py3_metadata_merge-0.1.0-py3-none-any.whl",
+      "url": "https://files.pythonhosted.org/packages/c7/b6/poetry_test_py2_py3_metadata_merge-0.1.0-py3-none-any.whl"
+    }
+  ],
+  "meta": {
+    "_last-serial": 0,
+    "api-version": "1.0"
+  },
+  "name": "poetry-test-py2-py3-metadata-merge",
+  "project-status": {
+    "status": "active"
+  },
+  "versions": [
+    "0.1.0"
+  ]
+}
diff --git a/tests/repositories/fixtures/legacy/json/relative.json b/tests/repositories/fixtures/legacy/json/relative.json
new file mode 100644
index 00000000000..807c063c1a3
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/relative.json
@@ -0,0 +1,47 @@
+{
+  "alternate-locations": [],
+  "files": [
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry-0.1.0-py3-none-any.whl",
+      "hashes": {
+        "sha256": "1d85132efab8ead3c6f69202843da40a03823992091c29f8d65a31af68940163"
+      },
+      "requires-python": ">=3.6.0",
+      "url": "poetry-0.1.0-py3-none-any.whl"
+    },
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry-0.1.0.tar.gz",
+      "hashes": {
+        "sha256": "db33179244321b0b86c6c3645225ff2062ed3495ca16d0d64b3a5df804a82273"
+      },
+      "requires-python": ">=3.6.0",
+      "url": "poetry-0.1.0.tar.gz"
+    },
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "poetry-0.1.1.tar.bz2",
+      "hashes": {
+        "sha256": "db33179244321b0b86c6c3645225ff2062ed3495ca16d0d64b3a5df804a82273"
+      },
+      "requires-python": ">=3.6.0",
+      "url": "poetry-0.1.1.tar.bz2"
+    }
+  ],
+  "meta": {
+    "_last-serial": 0,
+    "api-version": "1.0"
+  },
+  "name": "poetry",
+  "project-status": {
+    "status": "active"
+  },
+  "versions": [
+    "0.1.0",
+    "0.1.1"
+  ]
+}
diff --git a/tests/repositories/fixtures/legacy/json/sqlalchemy-legacy.json b/tests/repositories/fixtures/legacy/json/sqlalchemy-legacy.json
new file mode 100644
index 00000000000..6e0289bc429
--- /dev/null
+++ b/tests/repositories/fixtures/legacy/json/sqlalchemy-legacy.json
@@ -0,0 +1,22 @@
+{
+  "alternate-locations": [],
+  "files": [
+    {
+      "core-metadata": false,
+      "data-dist-info-metadata": false,
+      "filename": "sqlalchemy-legacy-4.3.4-py2-none-any.whl",
+      "url": "https://files.pythonhosted.org/packages/41/d8/a945da414f2adc1d9e2f7d6e7445b27f2be42766879062a2e63616ad4199/sqlalchemy-legacy-4.3.4-py2-none-any.whl"
+    }
+  ],
+  "meta": {
+    "_last-serial": 0,
+    "api-version": "1.0"
+  },
+  "name": "sqlalchemy-legacy",
+  "project-status": {
+    "status": "active"
+  },
+  "versions": [
+    "4.3.4"
+  ]
+}
diff --git a/tests/repositories/link_sources/test_base.py b/tests/repositories/link_sources/test_base.py
index 50664734713..8dfba17ae0e 100644
--- a/tests/repositories/link_sources/test_base.py
+++ b/tests/repositories/link_sources/test_base.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from collections import defaultdict
+from functools import cached_property
 from typing import TYPE_CHECKING
 from unittest.mock import PropertyMock
 
@@ -12,6 +13,7 @@
 from poetry.core.packages.utils.link import Link
 
 from poetry.repositories.link_sources.base import LinkSource
+from poetry.repositories.link_sources.base import SimpleRepositoryRootPage
 
 
 if TYPE_CHECKING:
@@ -20,6 +22,16 @@
     from pytest_mock import MockerFixture
 
 
+@pytest.fixture
+def root_page() -> SimpleRepositoryRootPage:
+    class TestRootPage(SimpleRepositoryRootPage):
+        @cached_property
+        def package_names(self) -> list[str]:
+            return ["poetry", "poetry-core", "requests", "urllib3"]
+
+    return TestRootPage()
+
+
 @pytest.fixture
 def link_source(mocker: MockerFixture) -> LinkSource:
     url = "https://example.org"
@@ -99,3 +111,18 @@ def test_links_for_version(
         set(link_source.links_for_version(canonicalize_name("demo"), version))
         == expected
     )
+
+
+@pytest.mark.parametrize(
+    "query, expected",
+    [
+        ("poetry", ["poetry", "poetry-core"]),
+        (["requests", "urllib3"], ["requests", "urllib3"]),
+        ("lib", ["urllib3"]),
+        ("nonexistent", []),
+    ],
+)
+def test_root_page_search(
+    root_page: SimpleRepositoryRootPage, query: str | list[str], expected: list[str]
+) -> None:
+    assert root_page.search(query) == expected
diff --git a/tests/repositories/link_sources/test_html.py b/tests/repositories/link_sources/test_html.py
index 14451ea78dc..3ed7054f88b 100644
--- a/tests/repositories/link_sources/test_html.py
+++ b/tests/repositories/link_sources/test_html.py
@@ -9,12 +9,35 @@
 from poetry.core.packages.utils.link import Link
 
 from poetry.repositories.link_sources.html import HTMLPage
+from poetry.repositories.link_sources.html import SimpleRepositoryHTMLRootPage
 
 
 if TYPE_CHECKING:
     from tests.types import HTMLPageGetter
 
 
+@pytest.fixture
+def root_page() -> SimpleRepositoryHTMLRootPage:
+    names = ["poetry", "poetry-core", "requests"]
+    hrefs = [f'<a href="{name}/">{name}</a><br>' for name in names]
+
+    return SimpleRepositoryHTMLRootPage(f"""\
+<!DOCTYPE html>
+<html>
+    <head>
+        Legacy Repository
+    </head>
+    <body>
+    {"".join(hrefs)}
+    </body>
+</html>
+""")
+
+
+def test_root_page_package_names(root_page: SimpleRepositoryHTMLRootPage) -> None:
+    assert root_page.package_names == ["poetry", "poetry-core", "requests"]
+
+
 @pytest.mark.parametrize(
     "attributes, expected_link",
     [
@@ -60,6 +83,19 @@ def test_link_attributes(
     assert link.yanked_reason == expected_link.yanked_reason
 
 
+def test_hash_from_url(html_page_content: HTMLPageGetter) -> None:
+    anchor = (
+        '<a href="https://files.pythonhosted.org/packages/16/52/cafe/'
+        'demo-1.0.0.whl#sha256=abcd1234">demo-1.0.0.whl</a><br/>'
+    )
+    content = html_page_content(anchor)
+    page = HTMLPage("https://example.org", content)
+
+    assert len(list(page.links)) == 1
+    link = next(iter(page.links))
+    assert link.hashes == {"sha256": "abcd1234"}
+
+
 @pytest.mark.parametrize(
     "yanked_attrs, expected",
     [
@@ -146,24 +182,42 @@ def test_metadata(
 
 
 @pytest.mark.parametrize(
-    "anchor, base_url, expected",
+    "anchor, base_url, repo_url, expected",
     (
         (
             '<a href="https://example.org/demo-0.1.whl">demo-0.1.whl</a>',
             None,
+            "https://example.org/simple/",
             "https://example.org/demo-0.1.whl",
         ),
         (
-            '<a href="demo-0.1.whl">demo-0.1.whl</a>',
-            "https://example.org/",
+            '<a href="https://example.org/demo-0.1.whl">demo-0.1.whl</a>',
+            "https://example.org/files/",
+            "https://example.org/simple/",
             "https://example.org/demo-0.1.whl",
         ),
+        (
+            '<a href="demo-0.1.whl">demo-0.1.whl</a>',
+            "https://example.org/files/",
+            "https://example.org/simple/",
+            "https://example.org/files/demo-0.1.whl",
+        ),
+        (
+            '<a href="demo-0.1.whl">demo-0.1.whl</a>',
+            None,
+            "https://example.org/simple/",
+            "https://example.org/simple/demo-0.1.whl",
+        ),
     ),
 )
 def test_base_url(
-    html_page_content: HTMLPageGetter, anchor: str, base_url: str | None, expected: str
+    html_page_content: HTMLPageGetter,
+    anchor: str,
+    base_url: str | None,
+    repo_url: str,
+    expected: str,
 ) -> None:
     content = html_page_content(anchor, base_url)
-    page = HTMLPage("https://example.org", content)
+    page = HTMLPage(repo_url, content)
     link = next(iter(page.links))
     assert link.url == expected
diff --git a/tests/repositories/link_sources/test_json.py b/tests/repositories/link_sources/test_json.py
index 1f11d8b42d0..a66c017c6e5 100644
--- a/tests/repositories/link_sources/test_json.py
+++ b/tests/repositories/link_sources/test_json.py
@@ -2,7 +2,94 @@
 
 import pytest
 
+from packaging.utils import canonicalize_name
+from poetry.core.constraints.version.version import Version
+
 from poetry.repositories.link_sources.json import SimpleJsonPage
+from poetry.repositories.link_sources.json import SimpleRepositoryJsonRootPage
+
+
+@pytest.fixture
+def root_page() -> SimpleRepositoryJsonRootPage:
+    names = ["poetry", "poetry-core", "requests"]
+
+    return SimpleRepositoryJsonRootPage(
+        {
+            "meta": {"api-version": "1.4"},
+            "projects": [{"name": name} for name in names],
+        }
+    )
+
+
+def test_root_page_package_names(root_page: SimpleRepositoryJsonRootPage) -> None:
+    assert root_page.package_names == ["poetry", "poetry-core", "requests"]
+
+
+def test_attributes() -> None:
+    content = {
+        "files": [
+            # minimal
+            {"url": "https://example.org/demo-0.1.whl"},
+            # all (with non-default values)
+            {
+                "url": "https://example.org/demo-0.1.tar.gz",
+                "requires-python": ">=3.6",
+                "yanked": True,
+                "hashes": {"sha256": "abcd1234"},
+                "core-metadata": True,
+            },
+        ]
+    }
+    page = SimpleJsonPage("https://example.org", content)
+
+    assert page.url == "https://example.org"
+    links = list(page.links)
+    assert len(links) == 2
+
+    assert links[0].url == "https://example.org/demo-0.1.whl"
+    assert links[0].requires_python is None
+    assert links[0].yanked is False
+    assert links[0].hashes == {}
+    assert links[0].has_metadata is False
+
+    assert links[1].url == "https://example.org/demo-0.1.tar.gz"
+    assert links[1].requires_python == ">=3.6"
+    assert links[1].yanked is True
+    assert links[1].hashes == {"sha256": "abcd1234"}
+    assert links[1].has_metadata is True
+
+
+@pytest.mark.parametrize(
+    ("yanked", "expected"),
+    [
+        ((None, None), False),
+        ((False, False), False),
+        ((True, False), False),
+        ((False, True), False),
+        ((True, True), True),
+        (("reason", True), "reason"),
+        ((True, "reason"), "reason"),
+        (("reason", "reason"), "reason"),
+        (("reason 1", "reason 2"), "reason 1\nreason 2"),
+    ],
+)
+def test_yanked(
+    yanked: tuple[str | None, str | None],
+    expected: bool | str,
+) -> None:
+    content = {
+        "files": [
+            {"url": "https://example.org/demo-0.1.tar.gz", "yanked": yanked[0]},
+            {"url": "https://example.org/demo-0.1.whl", "yanked": yanked[1]},
+        ]
+    }
+    if yanked[0] is None:
+        del content["files"][0]["yanked"]
+    if yanked[1] is None:
+        del content["files"][1]["yanked"]
+    page = SimpleJsonPage("https://example.org", content)
+
+    assert page.yanked(canonicalize_name("demo"), Version.parse("0.1")) == expected
 
 
 @pytest.mark.parametrize(
@@ -77,3 +164,24 @@ def test_metadata(
     link = next(page.links)
     assert link.has_metadata is expected_has_metadata
     assert link.metadata_hashes == expected_metadata_hashes
+
+
+@pytest.mark.parametrize(
+    ("url", "repo_url", "expected"),
+    (
+        (
+            "https://example.org/files/demo-0.1.whl",
+            "https://example.org/simple/",
+            "https://example.org/files/demo-0.1.whl",
+        ),
+        (
+            "demo-0.1.whl",
+            "https://example.org/simple/",
+            "https://example.org/simple/demo-0.1.whl",
+        ),
+    ),
+)
+def test_base_url(url: str, repo_url: str, expected: str) -> None:
+    page = SimpleJsonPage(repo_url, {"files": [{"url": url}]})
+    link = next(iter(page.links))
+    assert link.url == expected
diff --git a/tests/repositories/test_legacy_repository.py b/tests/repositories/test_legacy_repository.py
index f9e264f2485..bc012f60d04 100644
--- a/tests/repositories/test_legacy_repository.py
+++ b/tests/repositories/test_legacy_repository.py
@@ -4,6 +4,7 @@
 import re
 
 from typing import TYPE_CHECKING
+from typing import Any
 
 import pytest
 import requests
@@ -490,10 +491,10 @@ def test_package_yanked(
 
 
 def test_package_partial_yank(
-    legacy_repository: LegacyRepository,
+    legacy_repository_html: LegacyRepository,
     legacy_repository_partial_yank: LegacyRepository,
 ) -> None:
-    repo = legacy_repository
+    repo = legacy_repository_html
     package = repo.package("futures", Version.parse("3.2.0"))
     assert len(package.files) == 2
 
@@ -522,7 +523,7 @@ def test_find_links_for_package_yanked(
     package = repo.package(package_name, Version.parse(version))
     links = repo.find_links_for_package(package)
 
-    assert len(links) == 1
+    assert len(links) == 2
     for link in links:
         assert link.yanked == yanked
         assert link.yanked_reason == yanked_reason
@@ -581,9 +582,7 @@ def test_get_redirected_response_url(
     repo = MockHttpRepository({"/foo/": 200}, http)
     redirect_url = "http://legacy.redirect.bar"
 
-    def get_mock(
-        url: str, raise_for_status: bool = True, timeout: int = 5
-    ) -> requests.Response:
+    def get_mock(*args: Any, **kwargs: Any) -> requests.Response:
         response = requests.Response()
         response.status_code = 200
         response.url = redirect_url + "/foo"
@@ -595,6 +594,36 @@ def get_mock(
     assert page._url == "http://legacy.redirect.bar/foo"
 
 
+def test_get_page_prefers_json(http: responses.RequestsMock) -> None:
+    repo = MockHttpRepository({"/foo/": 200}, http)
+
+    _ = repo.get_page("foo")
+
+    accepted = [
+        item.strip()
+        for item in http.calls[-1].request.headers.get("Accept", "").split(",")
+    ]
+    preferred = [item for item in accepted if "q=0" not in item.split(";")[-1]]
+
+    assert preferred == ["application/vnd.pypi.simple.v1+json"]
+    assert any("*/*" in item for item in accepted)
+
+
+def test_root_page_prefers_json(http: responses.RequestsMock) -> None:
+    repo = MockHttpRepository({"/": 200}, http)
+
+    _ = repo.root_page
+
+    accepted = [
+        item.strip()
+        for item in http.calls[-1].request.headers.get("Accept", "").split(",")
+    ]
+    preferred = [item for item in accepted if "q=0" not in item.split(";")[-1]]
+
+    assert preferred == ["application/vnd.pypi.simple.v1+json"]
+    assert any("*/*" in item for item in accepted)
+
+
 @pytest.mark.parametrize(
     ("repositories",),
     [