WordPress Plugin · v1.0.0 · Coming soon
Speed Autopsy
Your speed plugin broke something. Speed Autopsy performs the post-mortem and names the setting responsible — without touching a thing.
- WordPress 6.2+
- PHP 7.4+
- GPLv2+
- Read-only
Free core coming to the WordPress.org plugin directory. This page is the plugin’s official home.
You turned on a speed plugin. Now your menu won’t open, your checkout looks broken, or your fonts are gone — and you have no idea which setting did it.
Cache and optimization plugins make sites faster by combining and minifying files, deferring and delaying JavaScript, removing “unused” CSS, and lazy-loading images. When it works, it’s great. When it breaks something, it breaks silently — and the settings that caused it are buried across dozens of checkboxes. Even the plugins’ own “safe mode” just turns whole categories off and leaves you to bisect the rest by hand.
Speed Autopsy is the post-mortem. It finds what your optimizer broke, names the setting responsible, and tells you how to fix it — without touching a single setting itself.
- LiteSpeed Cache
- WP Rocket
- Autoptimize
- W3 Total Cache
- SiteGround Optimizer
- WP-Optimize
- Perfmatters
- FlyingPress
- WP Fastest Cache
How it works
Confirm the death, then name the cause.
Job one · Confirmed breakage
Prove something is actually broken
Speed Autopsy fetches your own pages and checks whether the combined and minified files your optimizer generates actually load. A combined stylesheet or script that is missing or empty is the single most common catastrophic failure — your page requests a file that isn’t there, so its styles or scripts silently vanish. That is not a hunch; it is a 404 with a URL on it.
- Every same-host combined file your optimizer generates, fetched and checked.
- A page that requests zero stylesheets is a structural critical on its own.
- CDN-hosted files are reported “not checked” — never fetched from someone else’s server.
A combined stylesheet is missing on 2 of 5 pages
LiteSpeed Cache detected · 5 pages scanned. CONFIRMED findings are fetched facts; ADVISORY findings name a risk, not a proof.
Confirmed breakage CONFIRMED
| /cart/ — combined CSS returns 404 /wp-content/litespeed/css/8f2ac41…css Every style in that bundle never loads. | |
| /shop/ — combined CSS is empty (0 bytes) Fix: clear the optimizer’s cache to rebuild it. If it keeps failing, exclude the offending file from combination. |
Risky settings enabled ADVISORY
| Remove Unused CSS Dropdown menus and cart drawers commonly break — styles only needed after a click are stripped. Page Optimization → CSS Settings → Remove Unused CSS → OFF | |
| Combine JavaScript Sliders and mobile menus commonly stop working when execution order changes. |
Job two · The named culprit
Name the setting responsible
It cross-references the settings you have enabled against a knowledge base of known-breakage patterns — Remove Unused CSS breaking dropdowns and cart drawers, Combine JavaScript killing sliders and menus, Delay JavaScript stopping the checkout, lazy-load hiding slider images — and tells you the symptom to look for and the exact setting to change. Then it stops, because the change is yours to make.
- The symptom in plain language — what you would actually see on the page.
- The exact setting path, in your optimizer’s own words.
- Dismiss with a note when a risk is deliberate: an audit record, not a silenced alarm.
Active on this site
| LiteSpeed Cache 6.5.2 · 14 settings read | |
| Perfmatters 2.9.1 · 6 settings read |
Capabilities currently ON
- Remove Unused CSS
- Combine JavaScript
- Delay JavaScript
- Minify CSS
- Lazy-load images
Read, never written
Speed Autopsy never changes a setting, deactivates a plugin, or clears a cache. Every fix it suggests is yours to apply.
Strictly read-only
It never changes a setting, deactivates a plugin, clears a cache, or modifies your site in any way. It reads and it fetches — that’s all. A diagnostic you can trust must never be a hand on the controls.
Confirmed is not advisory
A combined file that returns 404 is a fact — fetched, with a URL. A risky setting is an advisory: a named pattern that commonly breaks things, not proof that yours is broken. The report never blurs the two.
A diagnostic, not a fixer
It does not speed your site up, does not change your optimizer, and cannot guarantee a fix. It tells you what your optimizer appears to have broken and what to change. You stay in control of every change.
In the free build
Complete for diagnosing a site.
Nothing below is limited, metered, or unlocked by payment.
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Nine optimizers detected
The active ones are identified and their current settings read — never written — across three different storage shapes.
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Bundle-integrity scan
Every same-host combined file your optimizer generates is fetched and checked. Missing or empty is a confirmed critical.
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Known-breakage knowledge base
Each risky setting you have on, matched to the symptom it causes and the exact setting path to change.
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Up to 5 scanned pages
Front page always, plus your shop, cart and key landing pages — the ones where breakage actually costs money.
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Weekly automatic scan
Runs on its own via WP-Cron, with an email when new issues appear. Nothing runs on your visitors’ page loads.
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Findings report
Severity, plain-language symptom, the fix, and dismiss-with-note for the ones you have decided are deliberate.
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Site Health integration
The verdict surfaced inside WordPress’s own Site Health screen.
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WP-CLI
wp speed-autopsy scan / status — including --format=json, ungated and unmetered.
Free vs Pro
Pro adds the layer a server-side scan cannot see.
A PHP fetch sees the HTML and whether files load, but it never executes your JavaScript. Pro’s opt-in, admin-only collector catches the real errors and failed loads you hit while testing — correlated to the deferred or combined script that caused them.
| Capability | Free | Pro |
|---|---|---|
| Optimizer detection + read-only settings audit (9 plugins) | ✓ | ✓ |
| Loopback bundle-integrity scan (missing / empty combined files) | ✓ | ✓ |
| Known-risky-settings knowledge base with per-setting symptom and fix | ✓ | ✓ |
| Weekly scan + email on new findings, dismiss-with-note | ✓ | ✓ |
| Site Health test, WP-CLI (incl. --format=json) | ✓ | ✓ |
| Loopback self-check with honest “scan impaired” state | ✓ | ✓ |
| Scanned pages | 5 | Unlimited |
| Runtime JavaScript-error collector (opt-in, admin-only) | — | ✓ |
| Slack & webhook alerts | — | ✓ |
| White-label client report (print / PDF) | — | ✓ |
| REST / JSON endpoint for fleet dashboards | — | ✓ |
Pro · founder pricing
Pro
$79/yr
Agency
$199/yr
14-day trial, no card required. Annual, in US dollars. If a licence lapses you keep the features — only updates and support stop. Pro is sold and licensed through Freemius, the merchant of record.
Questions people ask.
Will it change my cache settings or clear my cache?
No. Speed Autopsy is strictly read-only. It reads your optimizer’s settings and fetches your pages; it never writes a setting, clears a cache, or deactivates anything. Every fix it suggests is for you to apply, in control, when you are ready.
How is this different from my cache plugin’s “safe mode”?
Safe mode turns whole categories of optimization off and leaves you to work out which specific setting was the problem. Speed Autopsy keeps everything on and tells you which individual setting is the likely culprit, with the symptom and the fix — and confirms real breakage by checking that your combined files actually load.
Which cache and optimization plugins does it support?
LiteSpeed Cache, WP Rocket, Autoptimize, W3 Total Cache, SiteGround Optimizer, WP-Optimize, Perfmatters, FlyingPress and WP Fastest Cache. It detects any of them that are active and reads the settings it understands; a couple store settings in a form it can’t read, in which case it relies on the page and asset scan.
It says a combined file is missing — what does that mean?
Your optimizer combined several scripts or stylesheets into one cached file, but that file returns an error or is empty. Your pages ask for it, so the styles or scripts it should contain never load. Clearing your optimizer’s cache usually rebuilds it; if it keeps failing, exclude the offending file from combination.
What can’t it see?
Three things, and it says so rather than pretending otherwise. If your server can’t fetch its own pages the page and asset scan can’t run — Speed Autopsy shows “scan impaired” rather than a false all-clear, and still checks your optimizer settings. Files rewritten to a CDN host are reported as “not checked” rather than fetched, to keep its outbound requests to your own server only. And a server-side fetch does not execute JavaScript, so it cannot observe a script that loads fine but errors at runtime — that is what the Pro runtime collector is for.
Does it slow my site down?
No. Scans run on demand or weekly via WP-Cron, fetch a handful of your own pages, and store compact findings. Nothing runs on your visitors’ page loads.
Bisecting checkboxes at 1am?
Toggle, purge, reload, repeat — that is how this normally goes, and it can take a whole evening. Speed Autopsy reads the settings, checks the bundles, and hands you the shortlist instead.