DirectlyDrop / Guides
File Transfer Tools
Check this browser's transfer APIs and calculate or compare a file's SHA-256 digest without uploading it.
Prepared by: DirectlyDrop · Editorial method: source code, tests, and primary technical sources · Updated: August 23, 2026 · 6 min read and tools
Local transfer tools
The diagnostic on this page checks WebRTC, File API, OPFS, and Web Crypto support in this browser. The SHA-256 calculator processes the selected file on this device without uploading it. Interactive controls appear when JavaScript loads.
What does the transfer diagnostic measure?
The diagnostic checks HTTPS, online state, WebRTC data channels, File API, OPFS, and service worker support in this browser. It checks local API availability only; it cannot test the other device, firewall, or an actual TURN route.
WebRTC data channel and File API failures prevent transfer. Missing OPFS may still allow small files, but the recipient will use more memory. Copying the result into a support request can help separate device issues from network issues.
How do I compare a SHA-256 digest?
Sender and recipient each select their copy and calculate SHA-256. Matching 64-character values indicate identical contents; even a one-bit change produces a different digest. A digest checks integrity but does not prove that a file is safe or trustworthy.
Web Crypto performs the calculation entirely in this browser. The selected file is not uploaded. To limit memory use, the tool accepts files up to 256 MiB; use a trusted operating-system command for larger files.
When should I use the result?
Opening a received everyday photo or document and checking its size is often sufficient. Software packages, backups, deliverables, and long-term archives benefit from a SHA-256 comparison.
Do not use a file when digests differ. Verify both selected copies and sizes, then retry in a new session. Report repeated mismatches through the Contact page with non-sensitive diagnostic details.