Why does Chrome send four browsers in the user-agent header?

Question

I am using Chrome in linux with Version 51.0.2704.63 (64-bit). I recorded a HTTP request of Chrome and here is part of the recording:

User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.63 Safari/537.36

Why does Chrome send four browsers in the user-agent field? Is this a countermeasure to obfuscate the browser version?

Answer 1

Presumably you mean the following four:

1. Mozilla/5.0 (X11; Linux x86_64)
2. AppleWebKit/537.36 (KHTML, like Gecko)
3. Chrome/51.0.2704.63
4. Safari/537.36

most Web browsers use a User-Agent string value as follows:

Mozilla/[version] ([system and browser information]) [platform] ([platform details]) [extensions].

• Mozilla is a byproduct of browser wars.

• AppleWebKit/537.36 is the platform used by your browser.

• Chrome/51.0.2704.63 is your browser

• Safari/537.36 was added for historic reasons, where Safari was treated differently.

You may wish to also read this history or this SO post