The second biggest gain.
THE PROBLEM IT SOLVES
Without caching, every visit rebuilds the page: querying the database, running code, assembling output.
That happens for every visitor, repeatedly, for a page that has not changed.
WHAT CACHING DOES
Stores the assembled page and serves the stored copy.
The work happens once rather than every time.
WHAT DIFFERENCE IT MAKES
Frequently dramatic. A page taking several seconds can serve in a fraction of one.
It also reduces server resource use, which matters if you are hitting limits.
THE KINDS OF CACHING
- Page caching: storing the finished page
- Browser caching: the visitor's browser storing files it already downloaded
- Object caching: storing database query results
FOR MOST SITES
Page caching produces almost all the benefit.
WHEN CACHING CAUSES PROBLEMS
Pages that must be different per visitor: carts, accounts, checkout.
Good caching excludes those automatically.
WHERE TO START
Enable a caching plugin. It is the highest-return change available to most sites.
