Compress image to under 1MB

Not more than 1 MB for each image. If the quality would become too low, the dimensions are reduced in proportion. HKU student registration card photo: JPG, 100 KB to 1 MB, width to height 4:5, plain background with only one colour. Up to 50 images can be processed at once.

Choose a requirement

Up to 1 MBNot more than 1 MB

Please choose the requirement of the website where you will upload the file. If it is not listed, choose “Custom” and enter the size in step 3.

Name

Photographs for exam forms and identity documents must be cropped to size with the correct background. Please use the passport size photo maker.

Upload images

You can also drag images here.

You can choose up to 50 images at a time. Supported formats: JPG, PNG, WebP, HEIC, GIF, BMP, AVIF.

Set file size and dimensions

File size

The maximum is 1 MB. Leave a box blank for no limit.

Format
Dimensions

The original width and height are kept.

Check and download

After you upload images, check each requirement here and download.

Official requirements

The tool above has been set to these requirements.

What to upload
Student card photo
File size
Not more than 1 MB
Dimensions
Not specified
Format
JPG
Other rules
  • HKU student registration card photo: JPG, 100 KB to 1 MB, width to height 4:5, plain background with only one colour.
  • PolyU student card photo: JPG, 200 KB to 1 MB; 1200 × 1600 pixels from a digital camera, plain light-coloured background.
  • HKBU student card photo: JPEG, 150 KB to 1 MB, square, 400 × 400 to 1200 × 1200 pixels, plain background.
Source
Last checked: October 2026

The minimum size and dimensions differ between universities; this page sets only the 1 MB limit. Universities may update their requirements each year, so please check the latest instructions.

1 MB and pixel dimensions

For the same file size, the more pixels an image has, the less data each pixel gets and the lower the quality. The table below counts 1 KB as 1000 bytes. For the two ways of counting KB, please see the explanation by National Institute of Standards and Technology (NIST).

DimensionsPixelsData per pixel
640×4803,07,20026.04 bits
1280×96012,28,8006.51 bits
2048×153631,45,7282.54 bits
4000×30001,20,00,0000.67 bits

How to use

  1. The tool above has selected “Up to 1 MB” in step 1 and filled in the file size, format and dimensions in step 3.
  2. Upload your images in step 2. You can choose several at once, or drag them into the upload box.
  3. In step 4, check the result for file size, dimensions and format. If an item is invalid, change the settings in step 3 as explained below the image.
  4. Download the image. Several images are downloaded together as one ZIP file. Then upload the file to the website.

Common reasons for upload failure

  • File larger than 1 MB: some websites count 1 KB as 1000 bytes and others as 1024 bytes. This tool uses the stricter 1000 bytes, so the file is within the limit either way. If an image with many pixels is still too large at 50% quality, this tool reduces its dimensions in proportion. If you have unticked “Reduce dimensions if the file is too large”, please tick it again.
  • Wrong format: this website accepts only JPG. Please choose that format in step 3. HEIC photographs from an iPhone are converted to the chosen format.