5 Free Image Converters That Keep Your Photos on Your Device

You need to change a WebP file to JPG so your phone gallery can open it, or turn a PNG signature into a JPG for a form upload. Most online converters ask you to upload the image to their server, which means a copy of your photo or document sits somewhere you don't control. The five tools below do the conversion right on your phone or laptop. They work offline after the page loads or as a desktop app, and none of them need a sign‑up or add a watermark.

1. Toolzo Image Converter (browser, client‑side)

Best for: Quick format switches on a phone for form uploads, signatures, and WebP images.

Toolzo's image converter loads the conversion engine inside your browser. After the page opens, you can disconnect the internet and the tool still works. It supports JPG, PNG, WebP, and other common formats as both input and output. A quality slider lets you control the trade‑off between sharpness and file size when converting to lossy formats like JPG. Your image never touches a server. No daily limit, no watermark. This is the fastest way to switch a photo format on your phone before uploading to an SSC or IBPS form.

Limitation: It does not support niche formats like BMP, TIFF, or HEIC directly. For HEIC to JPG, use the dedicated HEIC to JPG tool. Transparency in PNG is preserved, but converting to JPG fills the transparent area with white, which is standard for the format.

2. Squoosh (browser PWA, offline after first visit)

Best for: Converting an image while also resizing and seeing a live before‑after preview.

Squoosh is Google's open‑source image tool. It runs as a Progressive Web App and works fully offline after the first visit. It can open JPG, PNG, WebP, AVIF, and other formats, and export to any supported format. The live side‑by‑side preview lets you see exactly what the conversion does. You can also resize and compress in the same workflow.

Limitation: It processes one image at a time; no batch conversion. The interface is more technical than a simple format‑switch tool. It is image‑focused with no document or PDF features.

3. XnConvert (desktop, batch, fully offline)

Best for: Converting dozens or hundreds of images between formats on a laptop.

XnConvert is a free desktop app for Windows, Mac, and Linux. It supports over 500 image formats and can batch convert an entire folder of images at once. You set the output format, quality, and destination folder, and it processes everything locally. It is the most capable free option for bulk format switching.

Limitation: Requires installation. No mobile or browser version. The sheer number of options can overwhelm someone who just wants to convert a single WebP to JPG.

4. Mac Preview / Windows Photos (built‑in, offline, zero extra tool)

Best for: A single quick format change on a laptop with no extra download.

On a Mac, open the image in Preview, go to File > Export, and choose the output format (JPEG, PNG, TIFF, etc.) with a quality slider. On Windows, the Photos app can save a copy in a different format via the "Save as" menu, though format options are more limited. Both are offline, free, and already installed.

Limitation: Windows Photos offers limited output format choices. Mac Preview covers JPG, PNG, TIFF, and a few others but not WebP. Neither tool handles batch conversion or gives a live output size preview.

5. GIMP (desktop, open‑source, fully offline)

Best for: Converting an image while also editing it in the same tool.

GIMP is a free, open‑source image editor available on Windows, Mac, and Linux. Open any supported image, then File > Export As and choose the output format. For JPG, it shows a quality slider and estimated file size. It runs entirely offline and supports transparency properly. If you are already editing an image, converting the format is one step in the same session.

Limitation: It is a full photo editor with a learning curve. For a simple format switch, opening GIMP is overkill. It is best when you are already using it for other edits.

Which one to pick for Indian form uploads and sharing

If you are on a phone and need to convert a WebP image to JPG, or turn a PNG signature into a JPG for an SSC or IBPS form, Toolzo's image converter is built for exactly that. It loads in the browser, runs offline, and gives you a quality slider. If you want to see the output quality before downloading, Squoosh is excellent. For batch converting a folder of images on a laptop, XnConvert is the most capable free option. And if you are on a Mac with no browser handy, Preview will handle the common format switches without any extra tool.