Yt-Downlaoder

A YouTube downloader that behaves like an installed Windows app. One setup.bat, an IDM-style button on the video player, and downloads that run locally on your PC.

MIT licensed · Windows 10/11 · Chrome, Edge, Brave

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What it does

• Button on the player. A small download icon sits at the top-right of the YouTube player. Click it and the available qualities drop down — clicking one starts the download immediately.
• Instant quality list. Qualities come from the player already running in the page, so the menu opens in milliseconds instead of waiting on a network lookup.
• As fast as your line allows. Every stream is pulled through aria2c with 16 connections, and video and audio are fetched at the same time. On a fast connection a 1080p video is usually done before the page finishes buffering it.
• One progress bar for the whole job. Video and audio download in parallel, then merge. You see a single bar, then Combining video… a few seconds, then done — not one bar per stream.
• Pause, resume, cancel. ❚❚ freezes the download and keeps the partial file, ▶ picks it back up, ✕ stops it.
• Nothing is lost when you click away. The download is owned by the extension's background worker, so closing the panel or the popup — or opening a different tab — never interrupts it, and the panel reconnects to the running job when you open it again.
• Finished files listed. The last downloads appear under Already downloaded, each with a button that reveals the file in Explorer.
• Paste any link. The toolbar popup takes any YouTube URL, shows a thumbnail preview, and downloads video (up to 8K when available) or MP3 audio.
• Fully local. No accounts, no servers, no telemetry. The extension talks only to a helper on your own machine.
• One file installs it. setup.bat fetches whatever is missing, skips whatever is already there, and pairs itself with your browser — no copy-pasting IDs, no compiler, no admin rights.

Install

1. Download this project and unzip it anywhere — a portable folder is fine.

2. Run setup.bat (double-click; no administrator rights needed). It walks through six steps and shows a progress bar for anything it has to fetch:

   Step	What happens
   1 · Checking this PC	reports what is already installed, so a second run has nothing to do
   2 · Local helper app	copies the helper and the extension into %LOCALAPPDATA%\YtDownlaoder
   3 · Downloader tools	yt-dlp, aria2c, FFmpeg, FFprobe, Deno — only the missing ones are downloaded, and yt-dlp is updated on every run
   4 · Register with Windows	Installed apps entry and a Start Menu shortcut
   5 · Pair with your browser	writes the native-messaging manifest for the extension folder
   6 · Final check	prints the version of every tool

3. Load the extension once, using the folder setup prints at the end:

   Open chrome://extensions → turn on Developer mode → Load unpacked → pick

   %LOCALAPPDATA%\YtDownlaoder\extension
   

That's it — no ID to copy. An unpacked extension's ID is derived from its folder path, so setup computes the same ID Chrome will and pairs the helper with it in advance. Downloads go to Downloads\Yt-Downlaoder unless you change the folder in the popup.

Running setup.bat again is always safe: with everything in place it finishes in a few seconds and reports Already set up. Nothing needed changing on this PC.

After editing anything in this project's extension/ folder, run setup.bat again (it re-copies the files), then click Reload on Yt-Downlaoder in chrome://extensions and refresh the YouTube tab.

How it works

YouTube page                Chrome extension                 Your PC
┌──────────────────┐        ┌───────────────────┐        ┌──────────────────────┐
│ player button    │◄──────►│ background worker │◄──────►│ YtDownloadHost.exe   │
│ quality dropdown │  msgs  │  owns the job:    │ native │  spawns yt-dlp,      │
│ progress + files │        │  progress, pause  │  msgs  │  merges with FFmpeg  │
└──────────────────┘        └───────────────────┘        └──────────────────────┘

• Content script (extension/content.js) draws the in-page button and panel. It never downloads anything itself; it asks the worker and renders whatever state comes back.
• Background worker (extension/background.js) is the single source of truth for the running download. Any window can ask it for liveState and catch up, which is why the UI survives being closed. It also reads the page's own player through chrome.scripting.executeScript to build the quality list with no network call.
• Native messaging host (native-host/YtDownloadHost) is a small self-contained .NET app. Chrome starts it on demand and talks to it over stdin/stdout, so there is no local web server and no open port. It runs yt-dlp, parses its output into one monotonic progress value, and reports the real file name it wrote.
• Pause/resume across processes. Chrome starts a fresh host process for every request, so a pause click cannot reach the running download in memory. The host writes a tiny flag file that the downloading process polls, then suspends or resumes the yt-dlp threads. The partial .part file stays on disk, so resuming continues instead of restarting.

Why it's fast

Choice	Effect
aria2c as the downloader, -x16 -s16 -k1M	one stream arrives over 16 connections instead of one
Quality list read from the loaded player	menu opens instantly instead of a multi-second lookup
--concurrent-fragments 16, --http-chunk-size 10M	many fragments download in parallel when a stream is fragmented
Height selectors (bv*[height<=1080]+ba)	best stream for that resolution, no format-id lookup
--extractor-args youtube:skip=hls	skips a manifest fetch that is never used
--continue	a canceled or paused download resumes where it stopped
Format results cached per video for 10 minutes	reopening the menu costs nothing

If aria2c is missing for any reason the helper falls back to yt-dlp's own downloader — everything still works, just slower.

Project layout

setup.bat                     installer, repair and uninstaller in one file
extension/                    the Chrome extension (setup copies this to %LOCALAPPDATA%)
  manifest.json  background.js  content.js  common.js  popup.*  styles.css
native-host/YtDownloadHost/    C# native messaging host
native-host/publish/           the prebuilt helper that ships with the repo
scripts/make-icons.ps1         regenerates the icon set and app.ico

Build from source

You don't need to. native-host/publish/YtDownloadHost.exe is committed — a trimmed, self-contained single file, so setup.bat needs neither the .NET SDK nor .NET itself on the target PC.

To rebuild it after changing Program.cs (needs the .NET 8 SDK):

dotnet publish native-host/YtDownloadHost -c Release -o native-host/publish

setup.bat only builds the helper if native-host/publish/YtDownloadHost.exe is absent — and then it offers to install the SDK with winget first. After rebuilding by hand, run setup.bat again to copy the new exe into place.

Uninstall

Use Installed apps → Yt-Downlaoder → Uninstall, or run:

setup.bat /uninstall

That removes the helper folder, the browser registrations, the Start Menu shortcut and the registry entry. Downloaded videos are left alone. Then remove the extension from chrome://extensions.

Troubleshooting

Symptom	Fix
Setup needed — run setup.bat	The extension is loaded from a folder the helper isn't paired with. Run setup.bat again — it re-pairs whatever folder the extension is actually loaded from.
Yt-Downlaoder was updated. Refresh this page.	Normal after reloading the extension — refresh the YouTube tab.
No 4K/8K option	That resolution isn't offered for the video.
Downloads fail after working for weeks	Run setup.bat again; it updates yt-dlp, which YouTube changes break regularly.
Nothing happens on click	Confirm %LOCALAPPDATA%\YtDownlaoder\YtDownloadHost.exe exists, then re-run setup.bat.
Downloads feel slow	Check the final list in setup.bat — if aria2c is marked missing, re-run setup so it can fetch it.

Legal

Download only what you own or are allowed to download, and respect copyright, YouTube's terms and your local law. This project is not affiliated with, endorsed by, or connected to Google or YouTube.

License

MIT © 2026 Ahmad Farooq

Bundled tools keep their own licenses: yt-dlp (Unlicense), aria2 (GPLv2+), FFmpeg (LGPL/GPL), Deno (MIT). They are downloaded by setup.bat from their official release pages, not redistributed here.