Upload Failure 38: An Error Code With No Dictionary
You tried to upload a file and got back a bare number: failure 38, maybe "upload failed with error code 38." No URL, no hint, no link to a help page. Searching for it mostly returns unrelated results, because unlike HTTP status codes, numeric application error codes aren't standardized — each service, app, or SDK invents its own numbering.
So the honest answer up front: error 38 doesn't mean one universal thing. But in practice, when upload tooling reports codes in this range, the cause is overwhelmingly one of two things: a connection timeout or a connection reset mid-transfer. This guide covers what error codes like this are, why 38 usually maps to a dropped connection, and what to do about it — on any platform.
How Numeric Upload Error Codes Work
When an uploader says "error 38," that number was generated somewhere in a stack with several layers:
- The browser or OS network stack (timeouts, resets, refused connections)
- A transfer library (FTP/FTPS, WebDAV, tus, or a proprietary SDK)
- The application itself, mapping internal failures to its own code table
Some ecosystems do publish code tables — FTP status codes and curl's exit codes are documented, and individual products sometimes list their own. But a bare "38" from an upload dialog usually comes from that third layer, and without knowing the exact product, the number alone can't be decoded. What you can decode is the behavior around it, and that's where the pattern emerges.
Why Code 38 Is Usually a Timeout or Connection Reset
Across forums and bug reports, "upload failed, code 38" clusters around the same story: the transfer started, ran for a while, and died mid-stream. That signature points at the two classic mid-transfer failures:
Connection timeout. Something between you and the server stopped passing data — congested upstream bandwidth, WiFi interference, a VPN renegotiating. After a watchdog period with zero progress, a layer in the stack gives up and reports a coded failure. (If your error message literally says "stalled," see our upload stalled for 30 seconds, aborting guide — same failure mode, named.)
Connection reset. The connection was killed outright — a firewall or antivirus cutting long POST requests, a corporate proxy enforcing a body-size cap, a server-side or CDN timeout, or mobile data switching networks. The socket closes, the uploader surfaces it as a numeric error.
In both cases the number is cosmetic; the physics is the same: your file was in transit and the pipe broke.
How to Fix It: A Debugging Order That Works
- Note when it fails. Same file size or same elapsed time every attempt → timeout (watchdog or proxy limit). Random points → unstable connection. This one observation halves the search space.
- Try a much smaller file on the same service. If 1 MB succeeds where 500 MB fails, you've confirmed a mid-transfer break, not an auth or permission problem.
- Eliminate the usual network suspects: disable VPN, pause cloud sync and other bandwidth-heavy apps, switch WiFi to ethernet or move closer to the router. On mobile, stay on one network for the whole upload.
- Rule out local interception: temporarily disable antivirus real-time/web scanning; on a work machine, ask IT about proxy size caps or domain blocks.
- Check the exact conditions: different network entirely (phone hotspot) + different machine. If it fails only in one combination, you've found the layer responsible.
- Check the service's status page — server-side incidents produce the same symptom from the other end.
- Capture the evidence if it persists: the exact error string, file size, time to failure, network type, and OS. That's what any support team needs to decode their own code 38.
The Platform-Agnostic Prevention: Resumable Uploads
Whatever layer produced the code, the failure mode is the same: a single long upload request that must survive start-to-finish or report failure. The prevention is therefore also the same regardless of platform — use an uploader that doesn't work that way.
Resumable upload protocols (tus is the open standard) split the file into chunks, acknowledge each chunk, and resume from the last acknowledged point after any interruption. A timeout or reset then costs you a few seconds of retry, not the whole transfer. If you're building uploads yourself, our technical guide to building a file upload feature covers the design considerations.
For sending files today, QuickUpload works this way out of the box: resumable, tus-style chunked uploads that retry and resume through connection drops, so "error 38"-style mid-transfer failures simply don't end the upload. Transfers use TLS 1.3 in transit, files are encrypted at rest, and every share supports passwords, expiry dates, and download limits — no account needed up to 50 MB, or 100 MB free with an account.
Try quickupload.io for your next large file — and let the code 38s stay someone else's problem.