Each tool does one job and states its limits up front. The ones people use most: compress a PDF or image to an exact size (2 MB, 500 KB, any limit), read DMARC aggregate reports without forwarding them anywhere, check a Google Merchant feed or Shopify CSV before import, compare two supplier price lists, and developer checks (JWT, regex, cron, CSP, Unix time) that run in your browser. 37 tools are free with no limit; 115 more give 3 free jobs a day, 44 of them without an account.