How do I get the user agent with Flask?


I"m trying to get access to the user agent with Flask, but I either can"t find the documentation on it, or it doesn"t tell me.

Answer rating: 202

from flask import request

You can also use the request.user_agent object which contains the following attributes which are created based on the useragent string:

  • platform (windows, linux, macos, etc.)
  • browser (chrome, firefox, msie, etc.)
  • version
  • language
  • string (== request.headers.get("User-Agent"))

Note: As of werkzeug 2.0, the parsed data of request.user_agent has been deprecated; if you want to keep getting details you need to use a custom UserAgent implementation and set it as user_agent_class on a custom Request subclass, which is set as request_class on the Flask instance (or a subclass).

Here"s an example implementation that uses ua-parser:

from ua_parser import user_agent_parser
from werkzeug.user_agent import UserAgent
from werkzeug.utils import cached_property

class ParsedUserAgent(UserAgent):
    def _details(self):
        return user_agent_parser.Parse(self.string)

    def platform(self):
        return self._details["os"]["family"]

    def browser(self):
        return self._details["user_agent"]["family"]

    def version(self):
        return ".".join(
            for key in ("major", "minor", "patch")
            if (part := self._details["user_agent"][key]) is not None

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