SKP Converter is a browser-based tool that converts SketchUp (.skp) files down to an older SketchUp version. Upload a file, it reads the header version, you pick a target, and you download the converted copy. Files must be .skp and 100 MiB or smaller, and the full file is uploaded to the processor for each check or conversion.
Checking a file's version is free with no sign-in. Each signed-in account gets one free successful conversion. More come from a daily check-in reward (one per Beijing day, up to 3 unused, each expiring after 7 days) or Premium at $7 per month or $48 per year. It is an independent website, not affiliated with SketchUp or Trimble.
SketchUp users often cannot open a newer .skp file in an older release. SKP Converter lets them convert a file down to an older version in the browser, without installing software.