About the User Agent Parser
Every web request carries a user agent string that names the browser, the system and sometimes the device. The strings are long and confusing, with every browser claiming to be Mozilla and Safari. This parser reads one and tells you in plain words: the browser and version, the operating system and version, the device type (phone, tablet or desktop), the rendering engine and whether it looks like a bot or a command-line tool. Paste a string from your server logs, or press the button to read your own browser's. The parsing is done in your browser with simple pattern rules, and nothing is uploaded.
Updated October 2026
How to use the User Agent Parser
- 1Paste a user agent string into the box.
- 2Or press the button to use your own browser's string.
- 3Read the browser, operating system, device type and engine.
- 4Check the bot flag if you are reading server logs.
- 5Clear the box to try another string.
How to read a string
Look for the clues in order. The part in brackets names the system, such as Windows NT 10.0, Android 13 or iPhone with CPU iPhone OS 17_2. After it come engine tokens like AppleWebKit and Gecko, and the browser is usually named last, such as Chrome/120.0, Firefox/121.0 or Version/17.2 Safari.
Edge, Opera and Samsung Internet all contain Chrome in their strings, so the parser tests for them first. Tablets and phones are told apart by words like Mobile, iPad and the lack of Mobile in an Android string.
Modern browsers also send client hints, a separate set of headers with similar data, and are slowly trimming the classic string. Chrome, for example, shows the same minor version and a fixed OS string on many systems. So an old log can tell you much more than a new one, and a mismatch between the two sources is a fair sign of something unusual.
Where this helps
- Understanding which browsers visit your site from log files.
- Debugging a bug report that came with a user agent.
- Checking whether traffic comes from a crawler.
- Testing what a device emulator sends.
- Writing rules for analytics filters.
Related tools
See your screen's pixel size with the Screen Size Checker and your network address with What Is My IP. The HTTP Header Lookup explains the other request headers, and the Regex Tester helps you write patterns to match user agents in your own code. Remember that user agents are easy to fake.
Features
- Browser name and version
- Operating system and version
- Phone, tablet or desktop
- Rendering engine: Blink, WebKit, Gecko
- Bot and tool detection
- Reads your own browser with one click
- Private, no upload
Frequently asked questions
What is a user agent string?
It is a line of text a browser or app sends with every request to say what it is. Servers use it to tailor pages or count visitors.
Why does every string start with Mozilla/5.0?
For historical reasons. Early sites served better pages to Netscape, nicknamed Mozilla, so every browser added the word to avoid being treated as inferior.
Why does Chrome mention Safari?
Chrome is built on WebKit and later Blink, and it keeps Safari in the string for compatibility. This parser checks the more specific names first.
How accurate is detection?
It is good for mainstream browsers, but user agents can be changed, hidden or frozen. Chrome now reduces detail such as the exact OS version.
Can it spot bots?
It flags common crawlers and tools such as Googlebot, Bingbot, curl and wget. A malicious bot can pretend to be a normal browser.
Is detecting browsers by user agent a good practice?
Feature detection is better for changing behaviour in your code. User agents are fine for analytics and logs.
Does it send my user agent anywhere?
No. Reading your own string and parsing both happen in your browser.