Precompiled rules for User Agent Parser

202603 · active · verified Sun Mar 29

ua-parser-builtins provides a precompiled ruleset for the `ua-parser` library, aiming to decrease its initialization times. This package itself does not expose any API; it solely contains the data. The precompiled ruleset is released monthly, synchronized with the `uap-core` project's default branch. The current version is 202603, released March 2026.

Warnings

gotcha ua-parser-builtins has no direct API or functionality. It is purely a data package designed to be used by the 'ua-parser' library to speed up its initialization. Installing it alone will not provide user agent parsing capabilities.
Fix: Always install 'ua-parser' (e.g., `pip install ua-parser ua-parser-builtins`) to utilize the provided data.
gotcha For optimal parsing performance, especially with high-volume user agent strings, consider installing 'ua-parser' with its optional 'regex' or 're2' dependencies. Even with 'ua-parser-builtins' reducing initialization time, the underlying parsing engine within 'ua-parser' affects speed.
Fix: Install with `pip install 'ua-parser[regex]' ua-parser-builtins` or `pip install 'ua-parser[re2]' ua-parser-builtins`.
gotcha The versioning scheme for ua-parser-builtins is date-based (YYYYMM). This indicates a refresh of the underlying ruleset, but unlike semantic versioning, it doesn't directly signal API or functionality changes, as the package has no API. Users should be aware that frequent updates reflect new user-agent patterns.
Fix: Keep `ua-parser-builtins` updated regularly (e.g., monthly) to ensure the `ua-parser` library benefits from the latest user agent detection rules.

Install

pip install ua-parser-builtins Install ua-parser-builtins
pip install 'ua-parser[regex]' ua-parser-builtins Recommended: Install with ua-parser (regex backend)

Imports

parse
```
from ua_parser import parse
```
Imports are from 'ua-parser', as 'ua-parser-builtins' provides data, not direct API.

Quickstart

This quickstart demonstrates the usage of the `ua-parser` library, which is the consumer of the precompiled rules provided by `ua-parser-builtins`. Installing `ua-parser-builtins` along with `ua-parser` will reduce the initialization time of the parser.

from ua_parser import parse

# ua-parser-builtins implicitly provides the data used by parse()
user_agent_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
parsed_ua = parse(user_agent_string)

print(f"User Agent Family: {parsed_ua.user_agent.family}")
print(f"OS: {parsed_ua.os.family} {parsed_ua.os.major}.{parsed_ua.os.minor}")
print(f"Device Family: {parsed_ua.device.family}")

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