diff --git a/README.md b/README.md
index 3796f40..8c9399e 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,12 @@
-# bookmarklets
-bookmarklets never had a hub. 1. Lets collect all. 2. Define context URL scope /regex  3. have all in a little "smart bar" browser extension
+# Bookmarklets
 
-## compare: tampermonkey
+Bookmarklets never had a hub.
+
+1. Lets collect all.
+2. Define context URL scope/regex
+3. Have all in a little "smart bar" browser extension
+
+---
+
+- [YouTube popup player](./yt_popup_player.md "Open bookmark README")
+- [YouTube audio boost](./yt_audio_boost.md "Open bookmark README")
diff --git a/yt_audio_boost.md b/yt_audio_boost.md
new file mode 100644
index 0000000..8b56abd
--- /dev/null
+++ b/yt_audio_boost.md
@@ -0,0 +1,66 @@
+# YouTube audio boost
+
+This bookmark adds a slider to the video player (next to volume control) to give additional volume boost to the video player (also boosts ads volume though).
+
+When used, it will ask for the maximum volume boost (default `5`; minimum `2`) for the slider.
+
+> [!NOTE]
+>
+> Shows an alert box if the video or volume control elements couldn't be found.
+
+## Instructions
+
+Create a new bookmark with any name and use the following text as the URL (copy-paste).
+
+```javascript
+javascript:(()=>{"use strict";const m=document.querySelector("div#movie_player>div.html5-video-container>video");const v=document.querySelector("div#movie_player>div.ytp-chrome-bottom>div.ytp-chrome-controls>div.ytp-left-controls>span.ytp-volume-area");if(m==null||v==null)return alert("Couldn't find YouTube player");const x=Number(prompt("Max boost value","5")??5);const a=new AudioContext();const g=new GainNode(a,{gain:1});new MediaElementAudioSourceNode(a,{mediaElement:m}).connect(g);g.connect(a.destination);const l=document.createElement("datalist");l.appendChild(Object.assign(document.createElement("option"),{value:"1",label:"100%"}));const r=Object.assign(document.createElement("input"),{type:"range",min:String(Math.max(0,g.gain.minValue)),max:String(Math.min(Math.max(2,Number.isNaN(x)?5:x),g.gain.maxValue)),value:String(g.gain.value),step:"any",style:"color-scheme:dark;accent-color:#f44;color:#0f0;vertical-align:middle"});r.setAttribute("list",l.id="AudioBoost-notches");r.addEventListener("input",()=>{g.gain.value=r.valueAsNumber;},{passive:true});const c=document.createElement("label");c.title="Audio boost";c.append(r,l);v.insertAdjacentElement("afterend",c);console.debug("Audio boost",g,c);})();
+```
+
+The text is minified JavaScript, which executes when the bookmark is clicked (on the current page).
+
+## How it works
+
+1. Creates audio context, media element source (from `div#movie_player>div.html5-video-container>video`), and gain node
+2. Creates a slider with a tickmark at value `1` and styling to fit the UI
+3. connect audio notes: video → gain → output
+4. add elements to DOM (after `div#movie_player>div.ytp-chrome-bottom>div.ytp-chrome-controls>div.ytp-left-controls>span.ytp-volume-area`)
+5. logs container element and gain node to console (debug log level)
+6. ...
+7. profit
+
+---
+
+<details closed><summary>Click to show formatted JavaScript</summary>
+
+```javascript
+(() => {
+    "use strict";
+    const mediaElement = document.querySelector("div#movie_player>div.html5-video-container>video");
+    const volumeButton = document.querySelector("div#movie_player>div.ytp-chrome-bottom>div.ytp-chrome-controls>div.ytp-left-controls>span.ytp-volume-area");
+    if(mediaElement == null || volumeButton == null) return alert("Couldn't find YouTube player");
+    const maxVolume = Number(prompt("Max boost value", "5") ?? 5);
+    const audioContext = new AudioContext();
+    const gainNode = new GainNode(audioContext, { gain: 1 });
+    new MediaElementAudioSourceNode(audioContext, { mediaElement }).connect(gainNode);
+    gainNode.connect(audioContext.destination);
+    const list = document.createElement("datalist");
+    list.appendChild(Object.assign(document.createElement("option"), { value: "1", label: "100%" }));
+    const range = Object.assign(document.createElement("input"), {
+        type: "range",
+        min: String(Math.max(0, gainNode.gain.minValue)),
+        max: String(Math.min(Math.max(2, Number.isNaN(maxVolume) ? 5 : maxVolume), gainNode.gain.maxValue)),
+        value: String(gainNode.gain.value),
+        step: "any",
+        style: "color-scheme: dark; accent-color: #f44; color: #0f0; vertical-align: middle"
+    });
+    range.setAttribute("list", list.id = "AudioBoost-notches");
+    range.addEventListener("input", () => { gainNode.gain.value=range.valueAsNumber; }, { passive: true });
+    const label = document.createElement("label");
+    label.title = "Audio boost";
+    label.append(range, list);
+    volumeButton.insertAdjacentElement("afterend", label);
+    console.debug("Audio boost", gainNode, label);
+})();
+```
+
+</details>