File.io vs Filestack

File.io is an anonymous, one-time file-transfer service: uploaded files get a short-lived link that self-destructs after a configurable number of downloads, with a simple REST API returning JSON for uploads and deletions. A live OPTIONS preflight with an Origin header against the real host, www.file.io, returned a 403 with no Access-Control-Allow-Origin header, resolving cors from unknown to no; no API key is required for basic use, and HTTPS was reconfirmed. A free anonymous tier covers casual transfers, while a paid plan raises file-size limits and adds account-based management.

Filestack is a file-upload and processing API that handles ingestion from local disk, cloud drives, and URLs, plus on-the-fly transformations like image resizing and document conversion. A live POST against the real gateway, www.filestackapi.com/api/store/S3, returned a 400 without a valid key, reconfirming API-key auth and HTTPS, and a follow-up OPTIONS preflight echoed the request Origin in Access-Control-Allow-Origin, resolving cors from unknown to yes. Filestack starts with a free plan for low-volume use and scales into paid Growth, Pro, and Enterprise tiers as upload and processing volume grows.