Built-In Ways to Convert Images on Mac, Windows and Android

The three platforms at a glance

The table summarizes what the sources I could verify say. Menu labels vary between versions, so read the entries as guides to where to look.

Platform	Built-in route	Formats offered	Several files
Mac	Preview, File then Export	HEIC, JPEG, JPEG-2000, OpenEXR, PDF, PNG, TIFF (more with Option key)	Yes, via the sidebar
Windows	Paint, File then Save as	Typically JPEG, PNG, BMP and GIF	One picture at a time
Android	No documented convert command	Varies by device and app	Not applicable

On a Mac: Preview

Apple documents the Preview route this way.

1. Start Preview and open the image in it.
2. From the File menu, choose Export.
3. In the Format menu, pick HEIC, JPEG, JPEG-2000, OpenEXR, PDF, PNG or TIFF.
4. Give it a name and location and click Save.

Apple adds that if the format you want is not listed, you can hold down the Option key while opening the Format menu to reveal more. JPEG and JPEG-2000 exports let you adjust the quality. For several files, Apple's guide says to open them together in one window, select them in the sidebar, and export the same way. That makes Preview the strongest built-in tool of the three. It also covers outputs the browser converter does not, namely TIFF and PDF.

What it does not show you is the result. There is no list of before and after sizes for the whole group, so you learn the file size by checking each file afterwards in Finder.

On Windows: Paint, and what to do about HEIC

Paint can open common formats and save them under another: open the picture, choose File, then Save as, and pick a format such as JPEG or PNG from the list. Saving as JPEG is how many people convert a PNG or WebP image on Windows 11. One quirk reported in Microsoft's Q&A forum is that clicking Save as directly may save a PNG, so hover over Save as and choose the format from the list that appears. Paint saves one picture at a time, so a folder means repeating the steps for every file.

HEIC is the other common Windows problem. Windows usually needs the HEIF Image Extensions, installed from the Microsoft Store, before File Explorer, Photos and other programs can show HEIC files, and some HEIC photos additionally need the HEVC extension; third-party guides report this, and I could not find a Microsoft page that states it as plainly, so check what your own system offers. Without the extensions, Paint will not open a HEIC file either. When the iPhone's sharing settings can be changed instead, the iPhone format guide covers where.

On Android: what is and is not available

The Android platform documentation lists which formats the system can decode: JPEG, PNG, WebP, GIF and BMP on all versions, HEIF from Android 9 (a device-optional feature, so some devices cannot), and AVIF from Android 12. That tells you what the phone can display. It does not tell you whether an app will offer to convert something, and I found no documented, built-in command in Android's own photo apps for saving a picture in a different format.

Behavior then depends on the manufacturer's gallery app and on Google Photos. Third-party reports say that downloading a HEIC photo from Google Photos gives you the original HEIC, and that saving the displayed preview from a web browser produces a JPEG at a lower resolution than the original. Treat both as reports to confirm on your own phone rather than as guarantees. If you need a different format and no app on the phone offers it, the browser route below is a practical fallback; the HEIC limitation described in the HEIC guide applies there.

When the browser converter is the better route

Many files. Paint converts one picture at a time. The browser tool takes up to 100 and returns a ZIP, with the details in the batch conversion guide.

Before and after sizes. Each result row shows the old and new file size, and the new pixel dimensions if they changed, so you see whether a conversion helped.

Resizing in the same step. The converter limits the longest side to a chosen value; Paint and Preview make you resize separately.

The same result on any device. A browser on a Chromebook, a phone and a desktop offers the same options and settings, which matters when you move between devices. Browsers can differ slightly in how they encode, so file sizes may vary a little, and HEIC opens only where the browser can decode it.

The system tools win in other cases. Preview exports TIFF and PDF, which the browser tool cannot produce. Paint is quick for a single file you are already editing.

A job compared: 40 saved WebP images to JPG

Suppose you have saved 40 pictures from websites and they arrived as WebP, which some programs and forms cannot use. On a Mac you open them in Preview, select all in the sidebar and export as JPEG once. On Windows, you repeat open, Save as, choose JPEG forty times. On Android, with no documented convert command in the system apps, you would need an app or a website. With a browser converter, you add all forty, choose JPEG and download one ZIP. Forty files is where the difference between "possible" and "practical" shows up.

For one or two files the calculation reverses: Paint or Preview opens immediately, with no page to load. Use whichever route has less friction for the job in front of you. A one-off conversion of a single picture rarely justifies installing anything. Quality still matters in either case, since every route that writes JPEG applies some compression, as the quality guide explains.

What none of the built-in routes tell you

Built-in tools convert the file and leave the consequences to you. They rarely tell you that a JPEG export discards transparency, that quality settings change the size, or that metadata such as location may or may not travel with the file, depending on the program and its options. Check the result in each case: open the new file, compare the size and look at a detailed area of the picture before you replace or delete anything.

Choosing the target format

The choice of output matters more than the tool. For photographs, pick JPEG and keep the quality setting high. For screenshots and graphics with text, pick PNG. If the picture has transparent areas, JPEG will fill them with a solid color, so PNG is the safer export, a point the transparency article takes further. Whenever a tool offers a quality control, use it, because default settings differ from program to program and the same picture can come out at very different sizes.