How to prepare a photo for an online application form

Do it in this order: crop to the required shape, resize to the required pixel dimensions, convert to the required format, and only then bring the file under the size limit. Each step changes the result of the ones before it, so any other order means starting again.

The quickest route here: Crop image for the shape, Resize image for the dimensions, Image converter if the format is wrong, and Resize image in KB last for the size. All four run in your browser, so the photo page of your passport never leaves your device.

What the form is actually checking

A rejection message is usually one line, but behind it there are four or five separate tests:

Test	Typical requirement	Fix with
Shape	35 × 45 mm, 2 × 2 in, 3:4	Crop image
Pixel dimensions	413 × 531, 600 × 600, "at least 200 × 200"	Resize image
File format	JPG only, sometimes JPEG or PNG	Image converter
File size	Between 20 KB and 50 KB	Resize image in KB
Content	Plain background, face visible, no filter	Retake the photo

1. Crop to the right shape first

35 × 45 mm, 2 × 2 inches and 3.5 × 4.5 cm are not interchangeable: the first and third are the same 7:9 shape, the second is a square. Crop with Crop image to the ratio the form asks for, with the head centred and the framing it specifies — many identity photos require the head to occupy 70–80% of the height, with a small margin above the hair.

Cropping first matters because cropping is the only lossless step: the pixels you keep are copied at full resolution. If you resize before cropping, you throw away pixels you then need back.

If you prefer the apps already on the device: Windows Photos has ratio presets in its Crop tool and exact pixel dimensions under "Resize image" in the "See more" menu; macOS Preview crops a rectangular selection with Tools → Crop and resizes with Tools → Adjust Size; iPhone Photos and Android Google Photos crop to a ratio but cannot set pixel dimensions, so the resize step has to happen somewhere else.

2. Convert millimetres to pixels

Most portals state pixels. Some state millimetres and a resolution, which needs one calculation:

pixels = millimetres ÷ 25.4 × dpi

Requirement	At 300 dpi	At 600 dpi
35 × 45 mm	413 × 531 px	827 × 1063 px
2 × 2 in	600 × 600 px	1200 × 1200 px
3.5 × 4.5 cm	413 × 531 px	827 × 1063 px
25 × 35 mm	295 × 413 px	591 × 827 px
45 × 35 mm (landscape)	531 × 413 px	1063 × 827 px

Use Resize image to reach exactly those dimensions, with "keep aspect ratio" ticked since the crop already fixed the shape. If the numbers do not divide evenly, a one-pixel difference is normal and is accepted by every portal that states a range.

Note that almost every portal checks pixel dimensions, not the dpi value written inside the file. Changing that value alone does nothing. DPI explained covers why.

3. Get the format right

If the form says JPG, give it a real JPEG, not a PNG renamed. Image converter writes a genuine file with the right internal structure; renaming an extension does not, and a well-built upload form detects the mismatch.

Two format traps:

• HEIC. An iPhone saves HEIC by default, browsers cannot decode it, and most portals reject it. Set Settings → Camera → Formats to "Most Compatible" before taking the photo, or export a JPEG copy from the phone.
• Transparency. JPG cannot store it. A signature scanned with a transparent background becomes a signature on a white rectangle — which is usually what you want, but check it is white and not black.

4. Hit the size limit last

Only now bring the file under the limit, with Resize image in KB: enter the target and the tool searches for the highest quality that still fits. Resizing or converting after this step changes the size again.

Watch for a minimum as well. "Between 20 KB and 50 KB" is a very common requirement, and a file that is too small is rejected just as firmly as one that is too big — this happens easily with a plain-background portrait, which compresses very well. The same tool can pad a file back above a minimum without touching the picture.

Signatures and other extra uploads

Portals that ask for a photo usually ask for a scanned signature too, under its own, much smaller limit. Sign in dark ink on plain white paper, photograph or scan it straight on, crop tightly to the ink with Crop image, and expect to hit the minimum size problem rather than the maximum.

Common reasons a photo is refused

The background is not plain. Most identity photos require a uniform light background. A wall at home rarely qualifies, because shadows count as texture and automatic checks measure the variation across the background.

The photo arrives sideways. Phone photos carry an orientation tag in their EXIF data. Your laptop honours it; some servers ignore it, so an upright picture arrives rotated. Rotate image writes the correct orientation into the pixels themselves, which no server can misread.

It is a photo of a photo, or a scan of a printout. Both add glare and moiré patterns that automatic checks flag as tampering.

It has been compressed too far. Below roughly 60% quality, blocks appear around the eyes and the hairline. If you cannot meet a tight KB limit at an acceptable quality, reduce the pixel dimensions instead — a smaller, clean photo beats a larger, blocky one.

The file name is the problem. Some older portals reject spaces, accented characters or very long names. photo.jpg always works.

What these operations do to the file

• Cropping copies the selected region at full resolution; nothing is resampled.
• Resizing down averages groups of pixels. It is the safest way to lose bytes.
• Every save re-encodes. A JPEG saved twice has been through the lossy step twice, so always start from the original rather than from yesterday's rejected copy.
• Metadata is dropped. The date, device model and GPS coordinates do not survive. If you want to confirm that before uploading an ID document, check with Remove image metadata or the metadata viewer.
• Nothing can be restored. Detail removed by compression is gone; raising the quality afterwards only makes a bigger file with the same defects.

Questions people ask

The form wants 200 dpi. How do I set that? Resize to the pixel dimensions that 200 dpi implies for the stated physical size. The dpi tag itself is rarely read.

Can I use a phone selfie? Often yes, if the background is plain, the lighting is even and the phone is held at eye level and about an arm's length away. Wide-angle front cameras distort features at close range.

Why does my photo look fine but keep failing? Check the requirement you have not tested: dimensions, minimum size, format, or a page limit on a PDF version of the same document.

Is anything uploaded when I use these tools? No. They run in the browser on your own device.

Next steps

• Meet an exact KB range: Resize image in KB
• Work out pixels from a physical size: DPI explained
• If the document rather than the photo is refused: Your file is too big for the upload form