JS concatenation means merging many script files into one large file so the browser makes fewer requests. That advice fit HTTP/1.1, when each file needed its own connection and extra requests were expensive. On HTTP/2 and HTTP/3, many small files share one connection, so one giant bundle often hurts more than it helps. A single change can bust cache for everything, and the browser may parse a large brick before it can paint the page.
Twenty small files with long cache lifetimes are often faster than one 800 KB file you rebuild on every deploy. The cost moved from connection count to parse time and cache invalidation. Fewer requests is not always faster. You get fewer cacheable pieces and a larger parse job before LCP can finish.
curl -sI https://example.com | grep -iE ‘HTTP/|server|content-type’If the status line shows HTTP/2 or HTTP/3, the old “combine everything” switch is solving the wrong problem. Next, check how many combine or minify plugins you have enabled. Three minifiers stacked often undo each other. A page builder that concatenates, minifies, and defers everything can delay the LCP image behind a heavy JS bundle. Logged-in users may get a different bundle, so the cache splits while logged-out LCP still looks slow.
Why stacked combine switches fail
Page-builder “combine CSS,” Autoptimize, LSCache, and a theme optimizer can all try to own the same files. Pick none of those combine options, or pick one owner and measure LCP after each change. Two plugins combining the same assets is a common way to ship a broken selector or a 404 for a hashed filename that only one tool created. A small critical CSS block inlined for the hero can still help. That is not the same as concatenating the whole theme into one file and hoping the rest defers cleanly.
Turn extras off, then measure
Disable combine on the extra plugins first. Keep minify only if the output stays sane. Keep LSCache in place on your LogicWeb account so pages still cache at the edge. Measure LCP on a phone while logged out. If one large file is still the bottleneck, split that file rather than concatenating more assets to keep it company. DevTools and the weight of the LCP request will show whether you are still optimizing for 2014. If a combine plugin already breaks checkout with a 500 error, turn it off on those URLs first, then revisit the homepage.
What to load instead
Load the CSS and JS each page actually needs. Let LiteSpeed and the browser multiplex the rest over HTTP/2 or HTTP/3. Prefer long cache lifetimes on stable files so a footer tweak does not force every visitor to re-download hero styles. When you change one script, only that script should invalidate. That keeps cache granularity useful and usually improves LCP more than one mega-bundle ever will.
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