WispFile

File transfer with no size limit

By the WispFile team · Updated 24 September 2026

Size limits exist because storing your file costs the service money; a direct transfer stores nothing, so it has no reason to cap size. What limits a big direct transfer instead is time (your upload speed), the receiver’s free disk space, and both devices staying online.

Key facts

  • No limit is set on WispFile transfers.
  • Verified end to end up to 5 GB so far, with an identical SHA-256.
  • Files stream to disk in small pieces, so memory stays flat.
  • The real limits: upload speed, disk space, staying online.

What actually limits a large transfer

LimitWhat to do
Upload speedCheck the time first: see the upload time table
Receiver’s disk spaceMake sure they have the size plus some headroom
Both devices onlinePlug in, turn off sleep
Network blocks direct connectionsTry another network, or Pro’s relay

What is verified today

We publish what we have measured. Transfers of 5 GB arrived with an identical SHA-256 while the receiver used under 10 MB of memory, because files stream to disk in 256 KB pieces instead of loading into memory. Nothing in that design changes with size, and larger runs are on our test list. For very large transfers, send a small test file first.

More detail: how long big uploads take and sending 50 GB.

What happens with a really large file

A browser can handle a file far larger than its memory, as long as nothing tries to load it all at once. WispFile reads the sender’s file one 256 KB piece at a time, and the receiver writes each verified piece to disk as it arrives. In Chrome and Edge that is straight into the folder the receiver chose; in other browsers it streams through the browser’s own download, so it still never sits in memory.

Limits that are not ours

  • The receiver’s disk. They need the file’s size free, plus some headroom; resuming after a reload also keeps a copy in the browser until the file is complete.
  • Old USB drives. FAT32 cannot hold a single file over 4 GB. exFAT, NTFS and APFS have no practical limit.
  • Many small files. One transfer holds up to 1,000 files; for more, zip them into one archive or send in batches.
  • Time. See the upload time table: at 20 Mbit/s, 100 GB takes about 11 hours.

Frequently asked questions

Is there really no size limit?

None is set. Practical limits are time, disk space and keeping both devices online.

What is the biggest file tested?

5 GB end to end so far, with a matching SHA-256.

Does a huge file use a lot of memory?

No: it is written to disk in 256 KB pieces as it arrives, so memory stays flat.

Can I send 100 GB?

No limit is set, and the design does not change with size. It takes time (about 2.2 hours at 100 Mbit/s of upload) and both devices online throughout. Test with a small file first.

Why do other services cap file size?

Because they store your file, and storage and bandwidth through their servers cost money. A direct transfer uses neither.

Related guides

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