Standalone · upload a browser HAR capture for a plain-language read-out. Runs entirely in your browser — nothing is uploaded.
Drop in a .har file exported from browser DevTools and this page tells you, in plain language, whether it's a slowness problem or an error problem — where time went, which requests failed, the referring pages, and the biggest and slowest resources.
To export: open DevTools → Network tab, reproduce the issue, then right-click the request list → Save all as HAR with content.