How to Convert PNG to WebP on iPhone Without an App

Someone tells you WebP files are smaller, so you go looking for a way to make one on your iPhone, and you find a wall of App Store listings that all want a subscription to do a thing that should take two seconds.

Before you install any of them, two things are worth knowing. First, iOS genuinely does not have a WebP converter built in, so this is one of the few image jobs with no local answer.

Second, for a large share of the people searching for this, WebP is the wrong target and something simpler solves the actual problem.

I build Grabio, a free Shortcut that does image conversion on-device using Apple’s own tools, and WebP is one of the formats I cannot do that way. Rather than hide that, here is the full picture: when you actually need WebP, what the working route costs you, and when to skip it entirely.

First, check whether you need WebP at all

This is the section that will save most readers the rest of the article.

If you are converting to WebP so a website loads faster, check what your platform already does. WordPress generates WebP versions of uploaded images in recent versions. Cloudflare, Shopify, Squarespace, Webflow and most modern hosts convert and serve modern formats automatically based on what the visitor’s browser supports.

In all of those cases, uploading a PNG and letting the platform handle it produces a better result than converting by hand, because the platform also handles the fallback for browsers that need one.

If you are converting because an upload form rejected your file, read the error again. Forms that reject a PNG are usually complaining about file size or dimensions rather than format, and WebP is rarely on their accepted list. Reducing the file size or resizing to exact dimensions is the actual fix, and both run on your phone.

If you are converting because a specific tool or client asked for WebP by name, carry on. That is a real requirement and the rest of this post is for you.

What iOS does and does not do with WebP

Reading WebP is fine. Safari displays WebP images on web pages without complaint, and Quick Look will show you one in the Files app. This has been true for several releases and iOS 26 is no different.

Creating WebP is the gap. Apple’s Shortcuts app has a Convert Image action, and it targets a fixed list of formats that Apple chose. WebP is not a format I can produce through it, and I have looked, because a one-tap on-device WebP converter is something I would ship immediately if the building block existed.

The Photos app has no export-as option at all. Files has no conversion menu. There is no first-party path, which is why every result you find for this recommends either an app or a website.

What Grabio converts on-device, and where WebP sits

Being precise about this matters more than making the tool sound bigger than it is.

Grabio is a free Apple Shortcut. There is no App Store install and no account. Its on-device photo conversions run through Apple’s own Shortcuts actions and cover JPG, PNG and HEIC, plus resizing, compressing, cropping to square, removing a background, stripping location data, and building a photo into a PDF.

All of that happens on your iPhone’s own processor, which is why those tools work in airplane mode.

WebP is not on that list, and it cannot be, because Apple does not expose it. So for WebP, Grabio does what it does for every other format outside its local set: it hands off to VERT, a free conversion site that covers 250 or more formats, with your file ready to drop in the moment it opens.

Be clear about the tradeoff. In this flow your file leaves your device. It gets uploaded to VERT for the conversion, which is different from how the on-device tools work. Either way the handoff goes straight to VERT.

That distinction is spelled out in converting any file format on iPhone, and it is the one place in Grabio where I have to tell people their file goes somewhere.

The steps, when WebP is genuinely what you need

1. Add Grabio to your iPhone once from Safari. It appears in your share sheet afterwards.
2. Open the PNG in Photos or Files and tap Share.
3. Scroll the share sheet and tap Grabio. If you do not see it, tap Edit Actions at the bottom of the sheet and pin it.
4. Because WebP is outside the on-device set, Grabio shows a short heads-up and offers to open VERT.
5. VERT opens in your browser with the file ready. Choose WebP as the output format and run the conversion.
6. Download the result. It lands in Files, under Downloads.

The converted file stays in Files rather than going to Photos, and that is correct behaviour rather than a bug. Photos does not import WebP. If you need it in your camera roll, you need a different format, which is the next section.

The alternative that is usually better

If your goal is a smaller file that works everywhere, JPG beats WebP on an iPhone almost every time, and I say that as someone who likes WebP on the web.

PNG is lossless. For a screenshot or a logo with flat colour that is exactly what you want. For a photograph it is a terrible container, and the file is enormous for no visible benefit.

Converting a photographic PNG to JPG typically collapses the size dramatically with no difference you can see at normal viewing size, it runs entirely on your phone, and the result imports into Photos, attaches to emails, and uploads to every form ever built. Converting PNG to JPG on iPhone covers it.

The one case where JPG cannot replace WebP is transparency. JPG has none. If your PNG has a transparent background and you need it to stay transparent in a smaller file, WebP is a legitimate answer and PNG optimisation is the other one. If transparency is what you actually care about, converting to PNG going the other direction is the more common need.

How to check what you actually got

After any conversion, confirm the result before you send it on. Open the Files app, long-press the file, and tap Get Info. It shows the file type and size. If the extension says.webp and the size dropped, the conversion worked. If the size barely moved, the source was probably already well compressed and WebP had nothing left to take.

If the share-sheet workflow sounds useful for the conversions that do run locally, Get the Shortcut. It is free, it installs in one tap from Safari, and you can open it in the Shortcuts app and read every action before you run it.

Converting PNG to WebP on iPhone: FAQ

Can I convert PNG to WebP entirely on my iPhone?

No. Apple’s Shortcuts actions do not produce WebP, and neither Photos nor Files has a conversion menu. Every route involves a website, which means the file leaves your device for the conversion.

Why will Photos not import my WebP file?

Because the Photos app does not accept WebP. Converted files land in the Files app under Downloads and stay there. Safari and Quick Look will display them, and your camera roll will not hold them.

Should I convert images to WebP before uploading them to my website?

Usually no. WordPress, Cloudflare, Shopify and most modern platforms generate and serve modern formats automatically based on the visitor’s browser, including the fallbacks. Uploading the original and letting the platform handle it gives a better result than a hand conversion.

Is WebP smaller than JPG?

Often, though the gap is smaller than the marketing suggests, and it depends heavily on the image. For a photograph on an iPhone, a JPG at sensible quality is dramatically smaller than a PNG, converts on-device, and works everywhere. That combination usually wins.

Does WebP keep transparency the way PNG does?

Yes, which is the one clear reason to choose it over JPG. If you need a transparent background in a file smaller than a PNG, WebP is a legitimate answer. If transparency is irrelevant to your image, JPG is simpler.

Is it safe to upload my image to a conversion site?

Treat it as handing a copy to someone else, because that is what it is. For an ordinary graphic that is fine. For anything sensitive, check first whether the job fits one of the conversions that run on your phone, since those never upload anything.