# How ReClip Handles Playlist Downloads: A Complete Technical Guide

> Discover how ReClip handles YouTube playlist downloads by processing each video individually server-side for efficient, reliable downloads. Learn the technical details.

- Repository: [Avery Gan/reclip](https://github.com/averygan/reclip)
- Tags: deep-dive
- Published: 2026-09-03

---

**ReClip processes YouTube playlists by extracting individual video URLs server-side and downloading each video separately, never as a single batch operation.**

This article explains how the [averygan/reclip](https://github.com/averygan/reclip) open-source tool implements playlist downloads. Understanding this workflow helps developers integrate ReClip's API or adapt its architecture for similar media downloader applications.

## The Two-Stage Playlist Download Architecture

ReClip splits playlist handling into **distinct enumeration and download phases**. This design prevents `yt-dlp` from treating the playlist as a single entity, which gives the frontend granular control over each item.

### Stage 1: URL Extraction via `/api/playlist`

When a client submits a playlist URL, the Flask server in [`app.py`](https://github.com/averygan/reclip/blob/main/app.py) invokes `yt-dlp` with specific flags designed for metadata-only extraction:

```python

# https://github.com/averygan/reclip/blob/main/app.py#L43-L63

@app.route("/api/playlist", methods=["POST"])
def get_playlist_info():
    data = request.json
    url = data.get("url", "").strip()
    ...
    cmd = ["yt-dlp", "--flat-playlist", "-J", url]
    result = subprocess.run(cmd, capture_output=True, text=True, timeout=60)
    info = json.loads(result.stdout)
    entries = info.get("entries", [])
    urls = [entry.get("url") for entry in entries if entry.get("url")]
    return jsonify({"urls": urls})

```

The **`--flat-playlist`** flag tells `yt-dlp` to return only basic entry information without fully extracting metadata for each video. The **`-J`** flag outputs machine-readable JSON. This combination completes quickly even for large playlists, returning a lightweight array of video URLs.

The response follows this structure:

```json
{
  "urls": [
    "https://www.youtube.com/watch?v=abc123",
    "https://www.youtube.com/watch?v=def456"
  ]
}

```

### Stage 2: Individual Video Downloads via `/api/download`

The client iterates through the returned URLs and initiates separate download requests. Each request spawns a background thread via the **`start_download`** function:

```python

# https://github.com/averygan/reclip/blob/main/app.py#L66-L84

@app.route("/api/download", methods=["POST"])
def start_download():
    data = request.json
    url = data.get("url", "").strip()
    format_choice = data.get("format", "video")
    format_id = data.get("format_id")
    ...
    thread = threading.Thread(
        target=run_download,
        args=(job_id, url, format_choice, format_id)
    )
    thread.start()
    return jsonify({"job_id": job_id})

```

The actual download worker enforces single-video behavior through a critical flag:

```python

# https://github.com/averygan/reclip/blob/main/app.py#L32-L38

def run_download(job_id, url, format_choice, format_id):
    ...
    cmd = ["yt-dlp", "--no-playlist", "-o", out_template]
    ...

```

The **`--no-playlist`** flag guarantees that even if a playlist URL somehow reaches this stage, `yt-dlp` downloads only the specific video referenced.

## Client-Side Implementation

The frontend in [`templates/index.html`](https://github.com/averygan/reclip/blob/main/templates/index.html) orchestrates the two-stage workflow. First, it retrieves the playlist members:

```javascript
// fetch playlist URLs
async function fetchPlaylist(url) {
  const res = await fetch('/api/playlist', {
    method: 'POST',
    headers: { 'Content-Type':'application/json' },
    body: JSON.stringify({ url })
  });
  const data = await res.json();
  return data.urls;          // array of video URLs
}

```

Then it processes each URL sequentially or in parallel:

```javascript
async function downloadPlaylist(url) {
  const videoUrls = await fetchPlaylist(url);
  for (const videoUrl of videoUrls) {
    const start = await fetch('/api/download', {
      method: 'POST',
      headers: { 'Content-Type':'application/json' },
      body: JSON.stringify({ url: videoUrl, format: 'video' })
    });
    const { job_id } = await start.json();
    // poll /api/status/:job_id and retrieve via /api/file/:job_id
  }
}

```

This separation enables **per-video progress tracking**, **individual error handling**, and **custom filename generation** for each download.

## Key Design Benefits

- **Resilience**: A single failed video does not abort the entire playlist
- **Progress visibility**: The UI can display status for each item independently
- **Flexible formats**: Each video can use different format selections
- **Clean filenames**: The `-o` output template in `run_download` ensures safe, predictable naming without playlist-induced path collisions

## Source Code Reference

| File | Responsibility |
|------|---------------|
| [[`app.py`](https://github.com/averygan/reclip/blob/main/app.py)](https://github.com/averygan/reclip/blob/main/app.py) | Flask routes for `/api/playlist`, `/api/download`, and download workers |
| [[`templates/index.html`](https://github.com/averygan/reclip/blob/main/templates/index.html)](https://github.com/averygan/reclip/blob/main/templates/index.html) | Frontend JavaScript consuming both endpoints |
| [`Dockerfile`](https://github.com/averygan/reclip/blob/main/Dockerfile) | `yt-dlp` installation and container configuration |

## Summary

- ReClip handles playlist downloads through **URL enumeration followed by individual video processing**
- The **`/api/playlist`** endpoint uses `yt-dlp --flat-playlist -J` for fast metadata extraction
- The **`/api/download`** endpoint always passes `--no-playlist` to prevent accidental batch downloads
- Each video receives its own **job ID** for independent tracking and retrieval
- This architecture prioritizes **reliability and user control** over download speed

## Frequently Asked Questions

### Can ReClip download an entire playlist as a single zip file?

No. The current implementation in [`app.py`](https://github.com/averygan/reclip/blob/main/app.py) explicitly prevents this. The `--no-playlist` flag in `run_download` forces single-video processing, and the API returns separate job IDs for each item. Users download files individually through `/api/file/:job_id`.

### What happens if a video in the playlist is unavailable?

The `/api/playlist` endpoint only extracts URLs, so unavailable videos still appear in the list. When the client requests `/api/download` for that specific URL, the `run_download` worker will fail and update the job status accordingly. Other playlist items continue processing normally.

### Is there a limit to playlist size?

The enumeration timeout is **60 seconds** as configured in `subprocess.run`. Extremely large playlists may hit this limit during the `/api/playlist` call. There is no explicit count limit, but practical constraints depend on `yt-dlp` performance and server resources.

### Can I modify ReClip to download playlists without the two-stage approach?

You would need to remove `--no-playlist` from `run_download` in [`app.py`](https://github.com/averygan/reclip/blob/main/app.py) and handle `yt-dlp`'s native playlist output directly. However, this would break the per-video progress tracking and error isolation that ReClip's architecture provides.