Impersonate option is not working in yt_dlp library

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Summary

The yt_dlp library’s impersonate option is not working as expected, resulting in a General error. This issue arises when using the nightly build 2026.01.06.233142 of yt-dlp with the curl-cffi installation.

Root Cause

The root cause of this issue is likely due to:

  • Incompatible curl-cffi version: The installed curl-cffi version may not support the specified impersonate target.
  • Invalid impersonate target: The impersonate target ‘chrome-116:windows-10‘ may be invalid or unsupported by the curl-cffi version.

Why This Happens in Real Systems

This issue occurs in real systems due to:

  • Version mismatches: Incompatible versions of yt-dlp, curl-cffi, or other dependencies can cause issues with the impersonate option.
  • Incorrect configuration: Incorrectly configured yt_dlp options, such as the impersonate target, can lead to errors.

Real-World Impact

The impact of this issue includes:

  • Failed downloads: The impersonate option is used to simulate a specific browser and operating system, which can be necessary for downloading certain videos.
  • Inaccurate metadata: Without the impersonate option working correctly, metadata extraction may not be accurate.

Example or Code

import yt_dlp
import json
import sys

# 1. Verify curl-cffi exists (Required for --impersonate)
try:
    import curl_cffi
except ImportError:
    print("Error: 'curl-cffi' is missing. Impersonation will not work.", file=sys.stderr)
    print("Fix: Run 'pip install \"yt-dlp[default,curl-cffi]\"'", file=sys.stderr)
    sys.exit(1)

url = "https://www.youtube.com/watch?v=somerandomid"
ydl_opts = {
    'quiet': True,
    'verbose': True,
    'format': 'best',
    'js_runtimes':{'deno': {}},
    'impersonate': "chrome-116:windows-10",
    'simulate': True,
    'skip_download': True,
    'noplaylist': True,
}

try:
    with yt_dlp.YoutubeDL(ydl_opts) as ydl:
        # Extract metadata
        meta = ydl.extract_info(url, download=False)
        # Safe extraction with defaults
        formats = meta.get('formats', [])
        duration = meta.get('duration')
        thumbnail = meta.get('thumbnail')
        title = meta.get('title')
        output_data = []
        for item in formats:
            if item.get('audio_ext') != 'none':
                # Add metadata to the specific format object
                item.update({'duration': duration, 'thumbnail': thumbnail, 'title': title})
                output_data.append(item)
                break
        print(json.dumps(output_data))
except yt_dlp.utils.DownloadError as e:
    # Specific check for impersonation target errors
    if "Impersonate target" in str(e):
        print(f"FAILED: The impersonate target '{ydl_opts['impersonate']}' is invalid or unsupported by your curl-cffi version.")
    else:
        print(f"yt-dlp download error: {e}")
except Exception as e:
    print(f"General error: {e}")

How Senior Engineers Fix It

Senior engineers fix this issue by:

  • Verifying dependencies: Ensuring that all dependencies, including curl-cffi, are up-to-date and compatible with the yt_dlp version.
  • Checking configuration: Reviewing the yt_dlp configuration to ensure that the impersonate target is valid and supported by the curl-cffi version.
  • Updating curl-cffi: Updating curl-cffi to a version that supports the specified impersonate target.

Why Juniors Miss It

Junior engineers may miss this issue due to:

  • Lack of experience: Limited experience with yt_dlp and curl-cffi can make it difficult to identify the root cause of the issue.
  • Insufficient testing: Inadequate testing of the impersonate option can lead to overlooking compatibility issues with curl-cffi.
  • Incomplete documentation: Incomplete or outdated documentation can make it challenging for junior engineers to understand the requirements and limitations of the impersonate option.