Why websites limit image file size (and how to meet the limit)
7 min read · Practical
The problem with large files
A modern phone camera produces photos that are 3-8MB each. For personal use, that is fine. For a website storing millions of user uploads, that is a serious problem.
Every uploaded file consumes storage, bandwidth and processing time. A job portal receiving 500,000 applications per year at 5MB per photo would need 2.5 terabytes of storage just for photos — and that is before backups, redundancy and serving the images to recruiters.
File-size limits exist to control these costs. They are not arbitrary restrictions; they are a practical engineering decision.
Where limits come from
Different systems set different limits for different reasons:
- Government portals often cap at 20-100KB because they were designed decades ago and never upgraded. The infrastructure was sized for small files and changing it is expensive.
- Job application systems cap at 100-500KB to keep the storage and processing budget predictable.
- University admission portals cap at 200KB-2MB depending on the number of applicants they expect.
- Visa applications have specific ranges (e.g. 240KB to 4MB for Canada) that balance identification needs against storage costs.
What the limit is actually about
When a form says "photo must be under 100KB", it is not asking for a low-quality photo. It is asking for a photo that is small enough to process cheaply but large enough to identify the applicant.
A 100KB JPG at 400×400 pixels is perfectly adequate for identification. The face is clearly visible, the resolution matches the display size, and the file fits comfortably within the system's budget.
The mistake many people make is uploading a 5MB photo and expecting the form to accept it, then discovering they need to compress it and having no tool that works.
How to meet a file-size limit
Meeting a file-size limit is straightforward once you have the right tool:
- Check the exact requirement. Some forms specify only a maximum (e.g. "under 100KB"). Others specify a range (e.g. "between 20KB and 50KB"). The range is more restrictive.
- Check the dimension requirement. Many forms specify both file size and pixel dimensions. A photo that is the right file size but the wrong dimensions will be rejected.
- Compress to the target. Use a tool that lets you set a specific target size and dimension.
- Verify the result. The tool should show you the final file size and dimensions.
Why local processing matters
Most online compressors upload your image to a server to process it. That is fine for a landscape photo, but it is a privacy risk for identity documents. A passport photo, a visa photo, a bank exam application photo — these are sensitive documents that should not be uploaded to a random server.
FITLY processes everything locally in your browser. Your image never leaves your device, never touches a server, and is never stored anywhere.
Try it now
Compress an image to a specific target size using the FITLY tool.