# Building a YouTube Downloader with Claude as Coding Help

Source: https://b-roll-6hk.pages.dev/blog/building-a-downloader-with-claude/
Published: 2026-09-25
Updated: 2026-09-25
Author: Ema Zamboni, video editor (https://b-roll-6hk.pages.dev/about/)
Section: Blog (https://b-roll-6hk.pages.dev/blog/)

**In short:** B-ROLL, a free Windows app that converts YouTube downloads into ProRes or DNxHR, was designed by video editor Ema Zamboni and coded with Claude as the coding assistant. Ema chose every feature from real editing needs and tested the app; Claude wrote and revised the code. The tools underneath, yt-dlp, ffmpeg and Deno, are open source.

## Who built B-ROLL?

B-ROLL was designed by a video editor and coded with Claude as a coding assistant. I am that editor, Ema Zamboni: I cut YouTube videos in DaVinci Resolve Studio on Windows 11, and I needed a faster way to collect b-roll for those edits. Claude, the AI assistant made by Anthropic, wrote the code.

The About dialog in B-ROLL tells the story in my own words: "I needed this app, so I made it with Claude since I'm not a developer. I tried to polish it and make it work as smooth as possible, but it may not be perfect." The installer credits the work as "Made by Ema Zamboni with Claude. Built on open-source software." The GitHub README is shorter still: "Vibe coded by Ema Zamboni with Claude."

The first build went up on GitHub on July 30, 2026, and [the first public release of B-ROLL](https://b-roll-6hk.pages.dev/blog/first-public-release/) covers what it could do on day one. More release notes and background posts live on the [B-ROLL Blog: Releases and Behind the Scenes](https://b-roll-6hk.pages.dev/blog/).

[Download B-ROLL for Windows](https://b-roll-6hk.pages.dev/download/): free, Windows 10 and 11 today, macOS and Linux planned. No account, no ads.

## What did the editor decide and what did Claude write?

The split in B-ROLL is simple: I decided what the app does and why, Claude wrote the code that does it, and existing open-source tools do the downloading and converting. Every feature started as a problem on my timeline, not as a programming idea.

The table shows who owns each part of the work.

| Part of the work | Who | What it covers in B-ROLL |
| --- | --- | --- |
| Features and priorities | Ema Zamboni | Clips by in and out points, ProRes and DNxHR conversion, creator credit files, subtitles |
| Code | Claude, as coding assistant | A Python and Tkinter app, packaged with PyInstaller as a Windows exe and with Inno Setup as an installer |
| Downloading | yt-dlp, an open-source project | Finding and fetching the YouTube streams |
| Converting | ffmpeg, an open-source project | Encoding the downloaded master into a ProRes or DNxHR `.mov` |
| JavaScript runtime | Deno, an open-source project | The JS runtime B-ROLL installs next to yt-dlp on first launch |
| Testing | Ema Zamboni | Real downloads cut on my own DaVinci Resolve timeline |

yt-dlp, ffmpeg and Deno are not written by Claude or by me. B-ROLL downloads them from their own GitHub release pages on first launch, and the [yt-dlp README](https://github.com/yt-dlp/yt-dlp) documents the downloader that sits under every B-ROLL download. For a plain-language profile of that tool, read [what yt-dlp is and whether it is safe to use](https://b-roll-6hk.pages.dev/compare/what-is-yt-dlp/).

## Which problems did B-ROLL have to solve on a real timeline?

B-ROLL had to solve three problems that came straight from my own edits, and each one changed how the app works. None started as a coding puzzle; each was a moment when downloaded footage did not behave in a real project.

**Footage that fought the timeline.** YouTube often delivers AV1 or VP9 video, and on my Windows 11 edit machine, 4K60 AV1 downloads were heavy to play back in DaVinci Resolve Studio. At times an AV1 or VP9 file crashed Resolve outright. B-ROLL's automatic ProRes and DNxHR conversion was built for exactly that: the file is downloaded first, then converted into an edit-ready `.mov`. The post on [how B-ROLL picks a ProRes or DNxHR tier automatically](https://b-roll-6hk.pages.dev/blog/how-codec-tier-auto-pick-works/) explains how the size of those files stays in check.

**The bot check.** At one point YouTube began refusing my downloads with "Sign in to confirm you're not a bot". The fix was a fresh cookies.txt, exported from a browser signed in to my own YouTube account and loaded in B-ROLL. Cookies expire, so as of September 2026 the message can still come back; the answer is to export the file again.

**Clips that stalled.** Clip downloads from deep inside long videos could stall. B-ROLL now prefers YouTube's HLS streams for clips, which fixed it, although the stream picked for a clip can differ from the one a full download of the same video would get.

## How was B-ROLL tested?

B-ROLL was tested the way an editor tests anything: by using it on real projects. I download footage with it and cut that footage in DaVinci Resolve Studio on Windows 11, so every feature has to survive a real timeline.

That kind of testing has limits, and B-ROLL says so. Its stated support is Windows 10 and 11 on 64-bit PCs; macOS and Linux are planned. The About dialog's own line, "it may not be perfect", is an honest summary of a tool built by one editor. When something breaks, the **Report a bug** button opens your email app with a message to me, and nothing is sent until you send it.

B-ROLL is also not code-signed, so Windows may warn you before the first run. Microsoft's [SmartScreen overview](https://learn.microsoft.com/en-us/windows/security/operating-system-security/virus-and-threat-protection/microsoft-defender-smartscreen/) explains that an app with no established reputation is marked as higher risk and gets a warning. The page on [whether B-ROLL is safe, with SmartScreen, signing and checksums](https://b-roll-6hk.pages.dev/troubleshooting/windows-smartscreen-warning/) walks through what to check before you choose to run it.

## What does an AI-assisted build mean for B-ROLL users?

An AI-assisted build means you get an editor's tool without the editor becoming a full-time programmer, and you should judge B-ROLL by what it does on your machine. Three facts matter more than who typed the code.

- **The source is not published.** B-ROLL is a free app built on open-source tools, and its own code stays private. You cannot read the B-ROLL code, but you can read the code of yt-dlp, ffmpeg and Deno, which do the downloading and converting. I answer the other common questions about what the app is and how it works in [the B-ROLL FAQ](https://b-roll-6hk.pages.dev/faq/).
- **Updates come from GitHub.** B-ROLL checks its GitHub releases for a newer version at launch, and yt-dlp updates itself to its latest nightly build every time the app starts. The updater does not check a signature or checksum, so compare the SHA-256 on the download page when you install by hand.
- **Nothing is sold to you.** B-ROLL is free, with no account and no ads; the **Support me** link opens a voluntary PayPal donation.

If you would rather see every option yourself, the command line is still there. The comparison on [choosing a yt-dlp GUI for Windows as a video editor](https://b-roll-6hk.pages.dev/compare/yt-dlp-gui-vs-command-line/) shows where a window like B-ROLL helps and where typing commands still wins.

> **Careful:** Download only footage you have the right to use: your own uploads, Creative Commons, licensed or permitted material.

## Frequently asked questions

Q: Is the source code of B-ROLL public?
A: No. The public B-ROLL repository on GitHub holds only a README, and the app ships as release files. B-ROLL is a free app built on open-source tools. The code of yt-dlp, ffmpeg and Deno, which do the downloading and converting, is public, and their licenses are listed on the page of [open-source credits and licenses](https://b-roll-6hk.pages.dev/open-source/).

Q: Is AI-written code safe to run?
A: Only when it comes from a source you can check, and that rule is the same for code written by a person. B-ROLL is not code-signed, so get it only from its GitHub releases, compare the SHA-256 checksum, and let your antivirus scan the file. The checksum for the current build is on the [B-ROLL download page](https://b-roll-6hk.pages.dev/download/).

Q: Will B-ROLL keep being updated?
A: Yes. Ema Zamboni plans further releases, including macOS and Linux builds. B-ROLL checks GitHub for a newer version 4 seconds after every launch. yt-dlp, the downloader inside, updates itself to its latest nightly build at each launch. There is no fixed release schedule, so the [B-ROLL changelog](https://b-roll-6hk.pages.dev/changelog/) is the record of what changed.

## Sources

1. [B-ROLL releases on GitHub](https://github.com/EmanueleZamboni/broll/releases)
2. [yt-dlp README on GitHub](https://github.com/yt-dlp/yt-dlp)
3. [Microsoft Defender SmartScreen overview (Microsoft Learn)](https://learn.microsoft.com/en-us/windows/security/operating-system-security/virus-and-threat-protection/microsoft-defender-smartscreen/)

---

B-ROLL is a free, donation-supported desktop YouTube downloader for video editors: it downloads videos, clips, playlists and channels, converts them automatically into edit-ready ProRes or DNxHR (or saves MP4, MKV, WEBM or audio), and includes built-in trimming, subtitles and automatic creator credit files. Part of [B-ROLL Blog: Releases and Behind the Scenes](https://b-roll-6hk.pages.dev/blog/) on the B-ROLL website. Download B-ROLL, free for Windows 10 and 11 (macOS and Linux planned): https://b-roll-6hk.pages.dev/download/