Best formats for online forms and uploads

The important thing to understand is that these checks are usually automated. A portal does not evaluate whether your document is good. It checks the file extension, the dimensions, and the byte count against a rule, and rejects anything outside it without explanation.

PDF is the format most commonly required by official portals. Government forms, legal submissions, and compliance documents are routinely expected in PDF because it preserves the exact layout and can be digitally signed. If a form asks for a “scanned document”, a PDF of your scan is almost always appropriate.

Where you have photographed a document rather than scanned it, image to PDF produces the expected container. For multi-page submissions, merging the pages into a single PDF is usually required; many portals accept one file per field, not several.

If a scan is grey, uneven or hard to read, the scan cleanup tools improve legibility before submission, and black-and-white conversion often reduces file size substantially on text documents.

For identity documents and photographs, JPEG is usually specified. Portrait photos for visa applications, for example, often come with precise resolution requirements, such as 600×600 pixels, and maximum file sizes.

It is worth reading the platform's requirements carefully. A photo that is even slightly outside the specified dimensions can cause an automated rejection, and the error message rarely tells you which rule you broke.

Where exact dimensions are specified, resize to those dimensions rather than relying on the portal to scale the image. Where a maximum file size is specified, use the target-size option in image compression and set it comfortably below the cap rather than at it.

Aspect ratio is the trap. Resizing a rectangular photo to a square target either distorts it or requires cropping. Crop to the correct ratio first, then resize to the exact pixel dimensions.

PNG is sometimes requested for documents that contain text or line art, where the sharpness of lossless compression is preferred over JPEG's smoothing. Some platforms also accept TIFF for scanned documents, though this is less common in consumer portals. FormatOS does not process TIFF: see supported formats for what is actually available.

Before converting anything, note down four things from the portal's instructions:

1. Accepted formats: and whether that means the extension, the actual file type, or both.
2. Maximum file size: per file, and any total across all uploads.
3. Exact pixel dimensions, if specified, and whether they are a minimum, a maximum, or exact.
4. Page or file count limits: whether multiple pages must be one file or separate ones.

Most rejections come from the third and fourth items, because people read the first two and stop.

FormatOS can help you hit specific format requirements, converting documents to PDF, resizing images to required pixel dimensions, or compressing files below a maximum size threshold.

However, each platform sets its own rules, and meeting those rules is the responsibility of the person submitting. FormatOS does not validate your file against any particular portal's requirements, because it does not know them. It gives you precise control over format, dimensions and size; deciding what those should be is your part.

One more limit worth stating: some portals require a digitally signed PDF or a specific PDF version such as PDF/A. FormatOS does not produce signed or PDF/A output. Where a portal demands those, a different tool is needed.

Open the converted file and look at it. Check that pages are in the right order, that nothing is cut off at the edges, and that text in a scanned document is actually readable at normal zoom. Automated portal checks do not catch a document that is upside down or missing its last page, but a human reviewer will, and by then the deadline may have passed. Rotate and reorder before uploading, not after rejection.