cHash is one of the most mysterious and misunderstood parameters in TYPO3. There are several articles about cHash on the web (including my own, see below) but it still remains a mystery.
cHash is important for proper caching in TYPO3. Therefore I decided to write when you need it and when not.
When to use cHash
You need cHash when:
- the content of the page depends on the parameter of the URL, and
- you do not use conditions, and
- you want the content to be cached
This typically happens in extensions. The extension must produce links with cHash if its output depends on the URL and the extension is of USER type.
When not to use cHash
You do not need cHash if:
- you create a USER_INT (non–cached) extension
- you generate different output using TypoScript conditions on the URL parameter
- you limit pages or site content to various user groups
In other words, care about cHash if you write PHP code. Forget cHash for the rest of TYPO3.