User-Agent & Client Hints Parser
Parse User-Agent strings, detect browser, OS, engine & device, audit bot crawlers & generate Client Hints
About User-Agent & Client Hints Parser
How User-Agent & Client Hints Parser Works
Analyzes HTTP User-Agent strings using high-performance client-side token regexes. Identifies browser vendor, version, operating system, device form-factor, CPU architecture, flags automated crawlers and AI bots, and formats corresponding Sec-CH-UA low- and high-entropy Client Hints without transmitting strings to any external server.
User-Agent & Client Hints Parser is a client-side web development, QA debugging, and analytics inspection utility designed to deconstruct and analyze HTTP User-Agent strings and modern Sec-CH-UA Client Hints. It breaks down complex, legacy-laden browser header strings into discrete, strongly typed fields: browser brand and major/minor version, operating system release and platform architecture, rendering engine (Blink, WebKit, Gecko, Trident), and device form-factor (Desktop, Mobile, Tablet, Bot/Crawler, Gaming Console, Smart TV). It includes automated bot identification for search engine spiders (Googlebot, Bingbot), AI web crawlers (GPTBot, Claude-Web, PerplexityBot, Bytespider), social link unfurlers, and CLI clients (cURL, Python Requests), complete with robots.txt directives and ready-to-use middleware snippets for Next.js, Express, and Python. Running 100% on-device, your browsing headers and test strings are never transmitted or logged.
Frequently asked questions
Why do modern browser User-Agent strings contain 'Mozilla/5.0' and 'AppleWebKit'?+
Because of historical browser compatibility wars. In the 1990s and 2000s, web servers inspected the User-Agent header and served degraded sites or blocked non-Netscape/non-WebKit browsers. To prevent site breakage, browsers began appending predecessor tokens ('Mozilla/5.0', 'KHTML, like Gecko', 'AppleWebKit/537.36'). DevToolkit Hub identifies these legacy camouflage tokens so you can distinguish true browser identity from historical noise.
What are User-Agent Client Hints (Sec-CH-UA) and how do they replace User-Agent strings?+
To reduce user fingerprinting and network payload size, Chromium browsers introduced structured HTTP headers known as User-Agent Client Hints (UA-CH). Low-entropy hints (Sec-CH-UA, Sec-CH-UA-Mobile, Sec-CH-UA-Platform) are sent automatically, while high-entropy details (model, platform version, bitness, architecture) are sent only if the web server explicitly asks for them using the Accept-CH response header.
How can I inspect my own live browser's User-Agent string?+
Click the 'Detect My Live Browser' button at the top of the tool. It instantly populates the input with window.navigator.userAgent without reloading the page or contacting an external server.
How do I block or permit AI crawlers like GPTBot and Claude-Web?+
Search engines and AI bots identify themselves in their User-Agent headers. You can allow or block them in your site's robots.txt file (e.g. 'User-agent: GPTBot' followed by 'Disallow: /') or detect them dynamically in Next.js Middleware using the code snippets provided in the Integration Snippets tab.
Is my User-Agent string transmitted to any server when I use this tool?+
No. The parser uses an embedded pure-JavaScript token regex engine executed 100% inside your browser. No strings, telemetry, or IP addresses are sent to any server.
Limitations
Because the User-Agent string is a client-provided HTTP header, clients (or proxy tools) can manually spoof or modify its contents.