Upload Errors and File Size Limits for Online Forms

Updated February 22, 2026 · 8 min read

An upload error is frustrating when the message is vague. Web forms often reject attachments above a set size, and the error message is not always clear about why.

Recommended settings for online forms

SettingStarting point
FormatJPEG (WebP where accepted)
Widthabout 1000 px on the long edge
Quality70
File size100 KB or less

These are practical defaults. If the platform or form you are using publishes its own limits, follow those instead.

Upload Errors and File Size Limits

Most errors come from three causes: the file is too big, the dimensions are outside the allowed range, or the format is not accepted.

For online forms, convert to JPEG, resize to about 1000 pixels and compress below 100 KB. If the form lists its own limits, use those numbers instead.

Step by step with TheCompressJPEG

  1. Open the compress JPEG to 100 KB tool, or the main compressor for custom settings.
  2. Drop in your image. Nothing is uploaded; it is processed in your browser.
  3. Set the maximum width to 1000 and the target size to 100 KB.
  4. Press Compress, check the result and download it.
Ready to try it? Compress your JPEG to 100 KB now. It's free and private.

Quick tips

  • Write a size limit slightly below the stated maximum to leave a margin.
  • Process private images locally rather than uploading them to unknown servers.
  • Crop out distractions so pixels go to the subject.
  • Use WebP where it is supported and you control the page.

FAQ

Can I compress images for e-learning courses without uploading them?

Yes. TheCompressJPEG runs entirely in your browser, so your images never leave your device.

Is WebP accepted for e-learning courses?

It depends on the platform. JPEG is the safest choice when you are not sure.

What size should an image be for e-learning courses?

A practical default is about 1600 pixels wide and 200 KB or less, unless the destination states its own limits.

Wrapping up

For online forms, the reliable recipe is simple: resize to around 1000 pixels, compress at quality 70 or to a 100 KB target, and check the result before you upload. Keep the original so you can always start again.

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