How to convert images in bulk (JPG, PNG, WebP) on Windows
Short answer
Windows has no built-in way to convert a whole folder of images at once. You can open each file in Paint and use Save as to pick a new format, which is fine for a few images. For a folder, use a batch converter. AppRig converts batches between JPG, PNG, WebP, BMP, GIF, TIFF, TGA and QOI in one pass, with optional resizing and quality control.
The manual way
Windows does not include a bulk image converter. To change one file’s format, open it in Paint, choose File > Save as, and pick a format such as PNG or JPEG. That is fine for a handful of images.
For a whole folder, say a camera roll or a set of exported assets, opening and saving every file one at a time quickly becomes a slog. Microsoft’s free PowerToys adds Image Resizer for batch resizing from the right-click menu, but it is built for resizing rather than format conversion. Free third-party tools such as IrfanView also have batch conversion modes.
The faster way with AppRig
AppRig’s Convert tool takes files or a whole folder dropped onto it, optionally including subfolders, and converts them in one pass between JPG, PNG, WebP, BMP, GIF, TIFF, TGA and QOI. Set the quality for JPG and WebP, or switch PNG and WebP to lossless. Optional resizing works by longest edge, exact size or percentage, with presets for common social sizes such as Instagram posts and YouTube thumbnails, and a choice to fit, squash or crop when the shape does not match.
Output can go to the same folder, a subfolder or one you pick. By default, if a file with the same name already exists, the new file gets a different name instead of overwriting it. Batches show per-file progress, can be cancelled, and failed files can be retried in one click. The free version converts up to 5 files at a time; AppRig Pro lifts the limit so a whole folder goes in one pass.
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Common questions
Does converting PNG to JPG lose quality?
Yes, a little. JPG is a lossy format, so some detail is thrown away to make the file smaller. At a high quality setting the difference is hard to see in photos, but sharp text, screenshots and line art can show blurry edges. JPG also has no transparency, so transparent areas become a solid colour. Keep screenshots and graphics as PNG or lossless WebP.
Should I use WebP instead of JPG or PNG?
For images on a website, usually yes. WebP files are typically noticeably smaller than JPG or PNG at similar visual quality, it supports transparency, and all modern browsers display it. Keep JPG or PNG when the images are going to older software, print shops or people who may not be able to open WebP, since some desktop apps still do not support it.
How do I resize a lot of images at once on Windows?
Windows has no built-in batch resize. Microsoft's free PowerToys adds Image Resizer, which lets you select images in File Explorer, right-click and resize them all to a preset size. If you also need to change format, or crop to exact social media sizes, a batch converter that combines resizing and conversion saves doing it in two passes.
Will a batch converter overwrite my original images?
It depends on the tool and where you send the output. The safest habit is to write converted files to a separate subfolder, or make sure the tool renames rather than overwrites when a file with the same name exists. Keep the originals until you have checked a few of the converted files.
Related questions
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