LiteSpeed cache compatibility

Settings → Markdown Alternate → Advanced

Adds a small block to your site’s .htaccess so requests that negotiate Markdown bypass the LiteSpeed page cache.

Default: off. Recommended on LiteSpeed hosts, and harmless everywhere else.

The problem it solves

A post’s permalink can return two different things — HTML or Markdown — depending on the Accept header the client sends. Telling caches about that is what the Vary: Accept header is for, and the plugin always sends it.

Whether a cache honours it is another matter. Some LiteSpeed configurations key their page cache on the URL alone and ignore Vary entirely. When that happens the cache already holds the HTML for that URL and answers from it, PHP never runs, and a client that asked for Markdown gets the HTML page.

Whether your particular host behaves this way cannot be detected from inside WordPress — it depends on the server configuration, not on anything the plugin can read. That is why this is a checkbox rather than something automatic, and why “enable it if unsure” is the safe advice: on a host that already honours Vary, the rule is simply redundant.

What the rule does

Requests whose Accept header mentions text/markdown skip the LiteSpeed cache, so PHP always decides which representation to send. Everything else is untouched: ordinary browser traffic stays fully cached, which is the whole reason you have the cache.

The block is wrapped in <IfModule LiteSpeed>, so on Apache, nginx or anything else it is inert. Enabling it on a non-LiteSpeed host costs nothing and does nothing.

It is written at the top of .htaccess, before WordPress’s own block — WordPress’s rules end the rewrite pass, so a block appended at the bottom would never be evaluated at all.

After enabling

Purge the LiteSpeed cache. Entries stored before the rule existed do not know about it, and stale entries are exactly the symptom you are trying to fix.

If .htaccess is not writable, the panel shows the block so you can paste it in yourself. Turning the setting off removes it again, and so does uninstalling the plugin.

What it does not do, and does not need to

It does not protect against Markdown being served to a browser. That cannot happen regardless of this setting: negotiated Markdown responses are sent with no-store, so no cache keeps a copy to hand out later. That protection is unconditional and works on every server.

This rule is about the other direction only — making negotiation work on a host whose cache would otherwise answer first. Safety is already handled; this is about function.

If you are not on LiteSpeed

Nothing here applies, but the underlying situation can. Behind a CDN, either add Accept to the cache key for your post URLs, or add a rule bypassing the cache when Accept contains text/markdown.

And the answer that works everywhere without configuration: use the .md URL. It is its own cache key, so no cache can confuse it with the HTML page.

See Markdown negotiation returns HTML for how to confirm what your host is actually doing.