You took a screenshot, or saved a logo, and a form or website says "JPG only". On iPhone, screenshots and many graphics are PNG files. PNG is great for sharp text and flat colors, but the files can be big, and some upload forms won't take them. This guide explains when PNG is the right format and when JPG is, what happens to transparent areas, and how to convert with Convert Cat, our photo and PDF converter for iPhone and iPad.
PNG or JPG: which one do you need?
Both are common image formats, and they're built for different jobs.
- PNG keeps every pixel exactly (it's lossless), and it can have see-through areas. That makes it good for screenshots, logos and graphics, but the files are often large.
- JPG (also written JPEG) throws away a little fine detail to make files smaller. It opens almost everywhere, which is why forms, email and many websites ask for it. It has no transparency.
So convert to JPG when a form insists on it, or when you want a smaller file for a photo-like picture. Keep PNG when you need a transparent background, or when the image is mostly text and sharp lines and size doesn't matter.
Convert PNG to JPG, step by step
- Open Convert Cat and pick your images. Tap Choose Photos for images in your photo library, or Choose Files for PNGs saved in Files or iCloud Drive. You can pick as many as you like, and you can mix PNGs with other images.
- Tap Convert format ("To JPEG, PNG or HEIC").
- Under Format, pick JPEG ("Opens everywhere"). It's already selected the first time you open the screen.
- Tap the button at the bottom, such as Convert 3 Photos.
On the result, tap Save to Photos, Save to Files or Share. Tap a file in the list to look at it before you send it.
You won't see the one-tap Convert to JPEG button for PNGs. That shortcut only shows up when every file you picked is an iPhone photo (HEIC). For PNGs, Convert format is the way in.
What happens to transparent areas
JPEG can't store see-through pixels. When a PNG has transparent areas, like a logo with no background, Convert Cat fills them with white in the JPEG. A dark logo on a clear background comes out as a dark logo on white.
If you need the background to stay clear, don't convert to JPEG. Under Format, pick PNG, or Keep original format, and the file stays a PNG.
Quality and size
JPEG files have a quality setting. On the Convert screen it starts at 90%, labelled Best. To change it, tap More options. Under File size, with Quality selected, move the slider toward the tortoise for smaller files or the sparkles for sharper ones; the label reads Best, High, Medium, Low or Smallest. The panel at the top shows about how big the files will be.
A JPG made from a screenshot full of small text can show soft or blotchy edges at low quality, so check it before you send it. If a form gives you a limit like "under 1 MB", tap Target size next to Quality instead. The full walk-through is in how to reduce photo file size on iPhone.
More options also has Pixels, if you want a smaller width and height too. Convert Cat remembers your last settings on this screen, so the next PNG is quicker.
What your converted files are called
Files you pick with Choose Files keep their names with a new ending, so logo.png becomes logo.jpg. Images picked with Choose Photos come in as Photo 1, Photo 2 and so on, and keep those names. If two files would end up with the same name, the second gets a number added.
With Convert Cat Pro you can choose Name them under More options instead, and set a pattern like Site-001, Site-002, numbered in the order you picked.
Hidden photo info
Further down the Convert screen is Hidden photo info. Images can hold where they were taken, the date, and the phone or camera, and anyone you send the file to can read it. Pick Remove location & photo info (where it starts, and "Recommended for sharing"), Remove location only, or Keep everything.
Your originals stay as they are
Convert Cat works on copies. Your PNGs in Photos and Files aren't changed, and Save to Photos adds the new JPGs as copies. The result shows the size before and after, how much smaller (or bigger) the files got, and "originals untouched". Finished conversions wait in the History tab, so you can save or share them again later.
Converting happens on your iPhone. The copies Convert Cat works on aren't uploaded or put in iCloud backup; a file leaves only when you save or share it.
What it costs
Converting PNG to JPG is free, for as many images as you pick, and so are quality, resizing and removing photo info. There's no watermark, no subscription and no account. Convert Cat Pro is an optional one-time unlock that adds four extras: Saved presets, Name your files, Shortcuts and Convert from the share sheet. More on the Convert Cat page.
Quick answers
How do I convert a PNG to JPG on iPhone?
In Convert Cat, tap Choose Photos or Choose Files, pick the PNG, tap Convert format, pick JPEG and tap the Convert button at the bottom.
Can I convert several PNGs to JPG at once?
Yes. Pick as many as you like; the button counts them, such as Convert 5 Photos.
What happens to a transparent background?
JPEG has no transparency, so Convert Cat fills those areas with white. To keep the background clear, keep the file as PNG.
Does converting PNG to JPG lose quality?
A little, because JPEG is lossy. Convert Cat starts at 90% (Best); lower quality makes smaller files with less detail. Tap the file on the result to check it.
Will my original PNG be deleted?
No. Convert Cat works on copies, so your originals are never changed.
Try Convert Cat
Try Convert Cat: free, no watermark, no sign-up → iyio.com/apps/convert-cat