I rebuilt my Windows video downloader from scratch — yt-dlp + FFmpeg + PyInstaller, 1,700 downloads later

Rebell Yell — Fri, 10 Jul 2026 19:01:14 +0000

Three months ago I posted here about Grabbit, a desktop video downloader I built for Windows. The app has grown a lot since then — new engine, local file converter, batch mode, transcript extraction — so I wanted to write a proper update with the actual technical details.

What Grabbit does (2026 edition)

Grabbit is a Windows 10/11 desktop app that downloads videos from 8+ platforms — YouTube, TikTok, Instagram, Facebook, Twitter/X, Pinterest, Twitch, SoundCloud — up to 4K quality. Everything runs locally. No cloud, no account required, no file upload anywhere.

It also ships with a local FFmpeg converter (Pro) that converts between video and image formats entirely on your machine.

Supported downloads: YouTube to MP3, TikTok, Instagram Reels, Pinterest, YouTube Shorts, SoundCloud, and more.

Supported conversions: Video → MP3, WebM → MP4, HEIC → JPG, WebP → JPG, Video → ProRes HQ, Video → DNxHR HQ.

The stack (unchanged from v1, for a reason)

Backend:      Python + Flask + yt-dlp + FFmpeg
Frontend:     Vanilla JS (no framework)
Auth/DB:      Supabase (PostgreSQL + Edge Functions)
Payments:     Stripe → Supabase Edge Function → Resend
Installer:    PyInstaller + Inno Setup
Distribution: GitHub Releases (auto-update via version check)

I kept the same stack because it works. The temptation to rewrite in Electron or Tauri was real but I resisted it. Adding complexity wouldn't have shipped any of the features below.

What's new: the FFmpeg Converter

The biggest addition since April is the local Converter. Users can drop a local file (MP4, MKV, AVI, MOV, WebM, HEIC, WebP) and convert it to another format — entirely on their machine. No upload, no size limit.

The trickiest part: bundling FFmpeg and pillow-heif with PyInstaller.

For FFmpeg I use imageio-ffmpeg which ships its own binary:

import imageio_ffmpeg
ffmpeg_path = imageio_ffmpeg.get_ffmpeg_exe()

This gives you a reliable path whether you're running from source or from a frozen PyInstaller bundle. No which ffmpeg nonsense, no PATH issues on Windows.

For HEIC support (pillow-heif), PyInstaller doesn't collect the native DLLs automatically. You need to force it in the .spec file:

# grabbit.spec
from PyInstaller.utils.hooks import collect_all
datas_heif, binaries_heif, hiddenimports_heif = collect_all('pillow_heif')

Without that, HEIC conversion silently fails at runtime on the packaged exe — no error, just nothing happens. Took an embarrassing amount of time to debug.

What's new: Batch mode

Pro users can paste up to 50 URLs at once — one per line — and Grabbit queues them all. The implementation is straightforward but the UX took iteration: users need to know which URLs failed and why, without it feeling like a wall of errors.

I ended up with a per-URL status row that shows queued → downloading → done/error in real time. The progress streaming still holds — polling every 600ms against a lightweight endpoint works well enough that I haven't needed WebSockets.

What's new: Transcript mode

Grabbit can extract transcripts from YouTube videos — useful for summarizing, repurposing content, or accessibility. It uses yt-dlp's subtitle extraction under the hood:

ydl_opts = {
    'writesubtitles': True,
    'writeautomaticsub': True,
    'subtitleslangs': ['en'],
    'skip_download': True,
}

Auto-generated captions aren't perfect but for most YouTube content they're good enough for summarization use cases.

What's new: self-updating yt-dlp

yt-dlp breaks constantly as platforms change their APIs. Rather than shipping a new app version every time, Grabbit updates yt-dlp silently in the background on launch:

import subprocess, sys

def update_ytdlp():
    subprocess.run(
        [sys.executable, '-m', 'pip', 'install', '--upgrade', 'yt-dlp'],
        capture_output=True
    )

When frozen with PyInstaller, sys.executable points to the bundled Python — so pip updates the bundled yt-dlp, not a system one. This means users always have a working downloader even when a platform changes something overnight.

Numbers after 3 months

1,700+ installs via GitHub Releases
Top countries: Mexico, US, Peru, Spain, Argentina, Colombia
Top traffic sources: Direct, Google Organic, ChatGPT referral
Free plan: 10 single downloads, 1 batch (up to 10 links), 2 transcripts
Pro: $8.99/month or $59.99/year — unlimited downloads, batch up to 50, all converter formats

The LATAM tilt was unexpected but makes sense in hindsight — there's a real gap for a clean Spanish-language download tool. I shipped 19 new SEO landing pages in Spanish last week targeting that.

What I'd do differently

Ship the Chrome Extension earlier. The extension puts a one-click Grab button directly on video pages while you're watching. It's one of the highest-retention features and I waited too long to build it.

Don't fight PyInstaller — embrace the spec file. I spent weeks trying to make things work without touching the .spec. The right answer is always: open the spec, add what you need, move on.

Ignore the "just use Electron" advice. Flask + Vanilla JS served from localhost is genuinely fine for a tool like this. The bundle is smaller, startup is faster, and I understand every line of it.

If you're building something similar — local desktop tool, Python backend, freemium model — happy to answer questions in the comments.

If you want to try it: appgrabbit.com — Windows only, free plan available, no account required.

I built a free desktop video downloader for Windows — Grabbit

Rebell Yell — Mon, 13 Apr 2026 00:40:24 +0000

I've been wanting to download videos from YouTube and TikTok for a long time, but every solution I found was either a sketchy website full of ads, a command-line tool that non-technical users couldn't use, or a bloated app that required an account and uploaded your files to a cloud server.
So I built my own.

What it does
Grabbit is a desktop app for Windows that downloads videos from YouTube, TikTok, Instagram, Facebook, Twitter, Pinterest, Twitch and SoundCloud — up to 4K/8K quality. It runs a local Flask server and opens in your browser, so the UI is just a web page served from localhost:5000. No Electron, no heavy framework. Just Python and Vanilla JS.
It also has a Chrome Extension that puts a Grab button directly on video pages. While you're watching a video, click Grab — it gets added to a download queue in real time. No copying links, no switching tabs.

How I built it
The stack is simple on purpose:

Backend: Python + Flask + yt-dlp + ffmpeg
Frontend: Vanilla JS SPA (no React, no Vue)
License system: Supabase (PostgreSQL + Edge Functions)
Payments: Stripe webhooks → Supabase Edge Function → Resend email
Installer: PyInstaller + Inno Setup
Distribution: GitHub Releases

The trickiest part was getting the download progress to stream in real time. yt-dlp outputs progress line by line, so I parse each line with regex and push it to a polling endpoint the frontend checks every 600ms. Not the most elegant solution but it works reliably.
Another challenge was packaging with PyInstaller. When frozen, file points inside the bundle temp directory, not where the exe lives. So I had to detect sys.frozen and use sys.executable to find the actual working directory. Took me longer than I'd like to admit.

What I learned

Building a freemium desktop app from scratch taught me a lot about things I'd never dealt with before — code signing certificates, Windows Smart App Control, subprocess encoding issues on Windows (cp1252 vs utf-8), auto-update architecture without breaking user data, and how to structure a license system that works offline when Supabase is unreachable.
The most important thing I learned: ship early. The first version was rough. But shipping it gave me real feedback and the motivation to keep going.

Where it is now

Grabbit is live. Free plan with 5 downloads/day. Pro plan at $8.99/month or $59.99/year for unlimited downloads, 4K/8K, all platforms, segment download and premium themes.

If you're curious: appgrabbit.com

Happy to answer any questions about the stack or implementation details.
If you try it, let me know what you think — feedback is welcome.

DEV Community: Rebell Yell