Topic guide

The complete guide to compressing photos and PDFs on iPhone

From 2MB and 500KB upload limits to HEIC-to-JPG and photos-to-PDF: pick the right method for each upload rule, then check format, pixels and file size.

When an upload fails, start with what the site asks for: format, file size and pixel dimensions are three separate conditions. Making a photo smaller does not fix a wrong format, and switching to JPG does not guarantee the size fits. Checking them in order saves more time than re-uploading again and again.

01Read the limits first, then choose a method

Note the maximum KB/MB, the width and height in pixels, the accepted formats, and whether there is a minimum file size. Treating KB and MB as 1,000-based is the safer choice. If exact dimensions are required, you may need to crop to the right ratio first; a "maximum width/height" rule only scales down proportionally and cannot produce an arbitrary ratio.

Article · PassSize What does a 1200x1200 photo size mean? Pixels, DPI and file size explained 1200x1200 means 1200 pixels wide and 1200 pixels tall; file size (KB, MB) is how much space the file takes. Upload sites check pixels and file size. DPI/PPI only matters for printing, and changing it won't make the file smaller. Article · PassSize Is 1MB 1000KB or 1024KB? How upload size limits are counted Both are in use: decimal 1MB = 1000KB, binary 1MiB = 1024KiB. When an upload site doesn't say which it uses, count in 1000s and leave a small buffer so the size check never blocks you. Article · PassSize Photo must be 300KB to 500KB but your file is too small? What to do A file that is too small usually has too few pixels or too much compression. Re-export from the original photo with higher JPEG quality and a larger pixel size and the file size will rise. Don't stretch a small image or pad the file by changing the format. Guide · PassSize How to crop a photo to exactly 600×800 without distorting it First crop in the Photos app at a 3:4 ratio, then resize to 600×800. With the same ratio, scaling stays proportional and faces aren't stretched or squashed. Don't force a photo of any ratio straight into 600×800.

02Photo too large: the 2MB and 500KB reading path

For ordinary attachments, start with the 2MB guide. For registration or ID photos, also check that the face is clear, the background is white and the pixels match. On iOS 26 you can resize in Preview and export JPEG; older systems can use a Shortcut. Built-in methods mean checking the file size again and again, while a tool that aims for a target size suits people who submit files often.

Guide · PassSize How to compress an iPhone photo to under 2MB Sign-ups, applications and document uploads often say "file must not exceed 2MB". Here are the built-in iPhone options, the pros and cons of each, and how to hit an exact size in one step with PassSize. Guide · PassSize How to shrink an application photo to under 500KB on your phone Application photos often require "under 500KB, set pixel dimensions, JPG format" all at once. Understand the three conditions, then use built-in iPhone tools or PassSize to get the photo under 500KB at the right size. Guide · PassSize How to batch-shrink photos and convert to JPG with an iPhone Shortcut (no app needed) Chain four actions in the built-in Shortcuts app: Select Photos > Resize Image > Convert Image (JPEG, set quality) > Save to Photo Album, to shrink several photos and convert them to JPG at once. The downside is you can't set a file size, so you check it yourself and lower the settings if it's over. Article · PassSize How does image compression work? Why do compressed images get blurry? Images get smaller in two ways, lowering JPEG quality (dropping subtle detail) and reducing pixel dimensions. Compress too much and you get blur and blocky patches. To hit a set size and keep your pixels, lower the quality first and only shrink the dimensions if that isn't enough.

03Format not supported: convert to JPG, then check the size

A photo already shot as HEIC has to be exported as JPG separately. Switching the camera to "Most Compatible" only affects new photos, and renaming the extension to .jpg is not a conversion. A JPEG can end up larger after converting, so check the upload limits again once you are done.

Guide · PassSize How to convert HEIC photos to JPG on iPhone Convert existing HEIC photos to JPEG with Quick Actions > Convert Image in Files, or export from the Preview app on iOS 26. To shoot JPG from now on, go to Settings > Camera > Formats and choose Most Compatible. Article · PassSize What is HEIC, and why do some websites reject it? HEIC is the iPhone's default photo format. At the same quality the file is smaller than JPEG, but many websites, upload forms, and some Windows PCs do not support it, so it often gets blocked. Converting to JPG before uploading fixes it. Article · PassSize Photo is under 2MB and a JPG, but the site still says wrong format? The most common cause is that the file is not really a JPG (for example a HEIC with just a renamed extension). Next: pixel size or aspect ratio mismatch, special characters in the file name, or a size right on the 1000/1024 boundary. Work through the checklist below and you will usually find it.

04Need a PDF: scan, merge and compress

Scan paper documents; for several photos, confirm the page order before combining them into one PDF. The size of a scanned PDF mostly depends on the page images, and compressing too far can make text hard to read. Zoom into every page before sending instead of looking only at the total size.

Guide · PassSize How to scan a paper document into a PDF on iPhone Both the built-in Notes and Files apps have Scan Documents. Point at the document, adjust the area and tap Keep Scan to save it as a PDF. To merge other files or compress to a set size, scan and process directly in PassSize. Guide · PassSize How to combine multiple photos into one PDF on iPhone Save the photos to Files from the Photos app, then in the Files app select them and choose Create PDF from the "..." menu to merge them into one PDF. To control page order, paper size or file size, use PassSize's photos to PDF. Guide · PassSize How to compress a large PDF on your phone PDFs are usually large because of the photos or scanned pages inside. iPhone's Preview app (iOS 26 and later) can shrink a file when exporting but can't hit a target size. To get under a hard limit like 2MB or 5MB, use PassSize to compress to an exact size on your phone.

05Handling private documents, and keeping a verifiable original

For IDs and contracts, prefer on-device tools, and find out how a file is stored before sending it to an online service. Removing GPS data, compressing and encrypting are different things, and a site with an upload form may have format limits of its own. Keep the original and work on a copy.

Article · PassSize Is it safe to upload ID photos to online compression sites? Online compressors upload your file to their servers. How long it is kept and whether it is analyzed depends on each site's policy. Fine for ordinary photos, but for IDs and contracts check the privacy policy first or use a tool that works on your phone. Guide · PassSize How to remove location data from a photo before sending it On iPhone, tap Options in the share sheet and turn off Location so the file you send carries no shooting location. You can also set a photo to "No Location" in Photos (reversible) or stop the camera from recording location at all. Article · PassSize Where to compress images: iPhone built-ins, websites, computers, and apps compared For the occasional single image, the iPhone's built-in Preview or Shortcuts is enough. To hit an exact KB target for an ID or contract, an app that processes on your phone and lets you set a target size is easiest. Here is how each option differs.

Check before you finish

The format is a JPG, PNG or PDF that the site accepts.
The file is under the maximum, and above the minimum if there is one.
Pixels, aspect ratio, page count and legibility are all checked.
The preview after uploading shows the file you just exported.

Related apps

Try the built-in methods first, then pick a tool based on how often you need it. Availability and features are listed on each app page.

PassSize

Compress documents and photos

Compress photos and documents fast so they fit upload size limits.

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