How to shrink an application photo to under 500KB on your phone

Quick answer

Application photo rules usually have three parts: file size (for example under 500KB), pixel dimensions (for example 600 wide × 800 tall) and format (mostly JPG). iPhone has no built-in “compress to 500KB” button. The free approach is to crop to the required ratio, then use the Preview app (iOS 26 and later) to resize to the required pixels, export as JPEG and lower the size with the Size slider, and finally check in the Files app that it’s under 500KB. To set the target directly, use an app that lets you specify a size, such as PassSize: choose a photo > set the target to 500KB and limit the dimensions if needed > save. It works on your phone, with no upload to a compression site.

Supported versions and screenshot notes

• The Preview method in this article applies to iOS 26. On iOS 18 you can use Shortcuts. Button names may change with minor system versions.
• PassSize requires iOS 18 or later and is still in App Store review, so it can’t be downloaded yet. The screenshots below are from a development build, using sample files to show where the controls are. They are not the result of this test.
• Submit the exported copy and keep your original. After cropping, converting and compressing, check the size again.

What rules do application photos usually have?

Requirements differ by organization, so always follow the official guidelines, but common conditions look like this:

• Maximum size: 500KB, 1MB and 2MB are most common. Occasionally there is a minimum such as “must not be smaller than XX KB”.
• Pixel dimensions: for example “600 pixels wide, 800 tall” or “at least 413×531”. Sometimes only the ratio is specified (for example 3:4).
• Format: JPG/JPEG is most common, some accept PNG, and HEIC is often rejected.
• Content: recent, facing the camera, white or light background, not heavily retouched, face clearly visible.

Note that “size” and “dimensions” are different: size is how many KB the file is, and dimensions is how many pixels the photo has. For how they relate, see What does a 1200×1200 photo size mean?

Why do phone photos often exceed 500KB?

iPhone photos are usually 12 megapixels or more, and a single photo is often 2-5MB, several times 500KB. The good news is that application photos usually need only a few hundred by a few hundred pixels, so shrinking the dimensions to what’s required makes the file much smaller on its own, and then a small tweak of JPEG quality gets it under 500KB.

Method 1: piece it together with iPhone’s built-in tools

• Crop: Photos app > open the photo > Edit > Crop. Crop out extra background and set the ratio the guidelines ask for (for example 3:4). Fewer pixels means a smaller file, but you can’t control the exact KB.

• Preview app (iOS 26 and later): first Share from Photos > Save to Files, then open it in Preview, tap More > Resize and set the pixels. Then from the menu beside the file name tap Export, choose JPEG and lower the file size with the Size slider. It works, but you have to keep checking that it’s under 500KB.

• Shortcuts app: build the resizing and JPEG conversion into a shortcut. This suits people who do it often. For setup, see How do I batch-shrink photos with an iPhone shortcut?

The built-in methods are free, but often take several tries. If you don’t know how many KB the result is, long-press the file in the Files app > Get Info to see its size.

Method 2: compress straight to 500KB with PassSize

PassSize is designed for uploads that have a size limit, so it fits the application scenario well:

• Pick 500KB as the target, or enter a custom size (for example a safer 450KB).
• It finds the highest usable quality that doesn’t exceed the target, so you don’t have to guess. The target is counted with 1000-based units and about 2% buffer is kept.
• You can limit the dimensions, for example 600×800, as a maximum pixel size. To get exact width and height, crop to the correct ratio first.
• HEIC can be converted to JPG along the way.
• Compression runs on your phone, so ID photos aren’t uploaded to a compression site.
• If it still can’t reach the target, the app tells you how many files are still over and suggests reducing the dimensions or changing the target.

You can also type something like “500kb” or “600x800 to JPG” and the app understands your limits. The steps are shown above.

Comparing the methods

Method	Can set 500KB	Can set pixels	Uploads the photo	Cost
Crop in Photos	No	Only through cropping	No	Free
Preview: resize + export	No (try with the slider)	Yes	No	Free (iOS 26 and later)
Online compression sites	Some can	Depends on the site	Yes	Mostly free with ads
PassSize	Yes	Yes	No	5 free uses, then NT$60 one-time purchase

To compare more tools, see Where should I compress images?

Tip: after compressing, zoom in on the face and background, then check “size, dimensions, format” against the guidelines one by one. Many rejections are because of a HEIC upload or the wrong pixel dimensions, not because the file was too big.

What we actually measured

On 2026-10-08, on the iPhone 16 Pro simulator, iOS 18.4, we tested using PassSize’s existing ImageProcessor compression engine. The input was a JPEG of gradient plus noise generated from a fixed seed, 4032×3024, 3,632,702 bytes. It is not a real portrait.

Target	Actual output	Output pixels	Target met
2MB (2,000,000 bytes)	1,938,809 bytes (about 1.94MB)	4032×3024	Yes
500KB (500,000 bytes)	489,408 bytes (about 489KB)	1933×1450	Yes

With the same test image, compressing to 2MB kept the original pixels, while compressing to 500KB reduced the dimensions. This shows that meeting the file size limit doesn’t mean keeping the original resolution, and guidelines with set pixel requirements still need to be checked separately. This is an engine test, not a full submission test on a real device, and it didn’t measure face or text clarity, so you can’t infer that every photo gets the same result. All 7 existing engine tests also pass, and invalid JPG input is correctly rejected.

Three common snags with 500KB submissions

• Under the maximum but below the minimum size: simply raising the target doesn’t necessarily enlarge the file. Re-export from the original with higher quality or the larger required pixel size, then test the size. Don’t force it by converting repeatedly at low quality.
• 600×800 turns into 600×400: limiting the maximum dimensions keeps the original aspect ratio and doesn’t stretch it to arbitrary pixels. Crop to 3:4 first, then export at the required width and height. Each application system has its own requirements.
• 489KB still can’t be uploaded: check the JPEG format, file name, minimum pixels and whether you chose the original file. File size is only one of the checks, and compressing smaller won’t fix a format error.

Official source and next steps

The built-in export method follows Apple: Export or compress images in Preview on iPhone. For other situations, pick a tutorial from the complete guide to photo and PDF compression.