This article describes several ways to check the character encoding information sent in the HTTP header of a web document.
It is important to clearly indicate the character encoding (charset) of a document served on the Web. Otherwise, a receiver may not correctly interpret the document. A Web browser, for example, may show random characters instead of readable text. One way of indicating the character encoding of a Web document is to put this information into the
charset parameter of the
In particular, it is important to note that the encoding declared in the HTTP header overrides all in-document encoding declarations in HTML and CSS files.
The Internationalization Checker tool, developed by the W3C, checks web pages for various internationalisation issues. It also has an information section that summarises key internationalization-related information about a page, such as character encoding and language declarations, etc. That section tells you whether an encoding declaration is used in the HTTP header, and if so, what is the encoding.
The i18n checker tool is particularly useful, since it also shows you other encoding declarations used in the document, and raises a flag if there are differences.
There are several services that show you all the HTTP headers and the (HTML) source of the document returned from the server after you enter the address of the document you are interested in:
Note: W3C has no relationship to any of these services.
In the HTTP headers, look for the
Content-Type header, and in particular for the
charset parameter, e.g.
Content-Type: text/html; charset=utf-8
charset parameter may not be present. This is okay if your document itself indicates its character
To check the markup, the Markup Validation Service has to make sure it correctly decodes the document it checks. It will show an error message if it cannot find information about the encoding, or if it finds conflicting information, or if it cannot decode the document according to the information it found.
To know the encoding that the validator found, you can use the extended interface.
In this interface, you can also select the show source option, and then visually check that the source is
correctly interpreted. This is useful to check that you actually use the right encoding. It is not always possible to mechanically check
whether for example, a document claiming to be
iso-8859-1 is actually encoded using
iso-8859-2 or some other encoding.
telnetor another command-line tool
This requires a bit more expertise, but may be easier to automate. Another command line tool may be
wget (with a
Some servers transcode the Web documents they serve to different character encodings for different clients. This happens for example with some servers in Russia. This requires special care, because your browser, running e.g. on a Mac or on a Windows system, may indicate using a different character encoding than the encoding given to you by a Web-based service or the W3C Markup Validation Service (which are mostly based on UNIX systems).