ConvertMaster

Free Universal Image Converter Convert, Crop & Resize 30+ Formats

ConvertMaster is a free universal image converter that runs entirely inside your browser. Use this free image converter to convert JPG, PNG, WEBP, AVIF, HEIC, RAW, PSD, EXR, HDR, JXL, and 30+ other formats without uploading a single file to any server — no account, no watermarks, no file size caps beyond your available RAM.

Convert images online whether you need to turn a photographer’s RAW file into a shareable JPEG, prepare social media graphics at the right dimensions, strip transparency before sending to print, or batch-convert a folder of images into modern WEBP format. This secure browser-based image converter keeps your files 100% private — your images never leave your device.

Built on a dual-engine architecture — a hand-written Pure JavaScript engine for instant standard conversions and an ImageMagick WebAssembly engine for professional formats — ConvertMaster is the most capable free image converter available in any browser, on any device.

Supported Input Formats

ConvertMaster can open and decode the following image types directly in your browser:

• Standard Web Formats: JPG / JPEG / JFIF, PNG, WEBP, GIF, BMP, SVG, ICO, AVIF — decoded natively by the browser, zero loading time.
• Apple Formats: HEIC / HEIF — decoded via the ImageMagick WASM engine or the heic2any fallback library, with no plugins required.
• Camera RAW Formats: CR2 (Canon), NEF (Nikon), ARW (Sony), DNG (Adobe), ORF (Olympus), RAF (Fujifilm), PEF (Pentax), RW2 (Panasonic), SR2 (Sony) — all decoded to a browser-safe preview via the WASM engine.
• Professional Design Formats: PSD (Adobe Photoshop), XCF (GIMP) — layers are flattened on import via ImageMagick WASM.
• HDR / VFX Formats: EXR (OpenEXR), HDR (Radiance RGBE) — high dynamic range images decoded and tone-mapped for accurate export.
• Next-Gen & Other Formats: JXL (JPEG XL), JP2 / J2K (JPEG 2000), DDS (DirectDraw Surface), TGA (Targa), TIFF / TIF, ICNS (Apple Icon), CUR (Windows Cursor), WBMP, PBM, PGM, PPM, PNM, EMF, WMF.

Supported Output Formats

• JPG / JPEG — Universal lossy photo format. Adjustable quality from 10% to 100%. Best for photographs and web images where file size matters.
• PNG — Lossless, full transparency support. The standard for logos, icons, and screenshots requiring pixel-perfect quality.
• WEBP — Google’s modern web format. Typically 25–35% smaller than JPEG at equivalent quality. Supported in all modern browsers.
• AVIF — Next-generation format offering 50%+ size reduction vs JPEG. Requires Chrome or Chromium-based browser for export.
• GIF — 256-color palette format. Useful for simple graphics and basic animations. Generated with a custom LZW encoder — no library dependency.
• BMP — Uncompressed Windows Bitmap. Maximum raw quality, large file size. Generated with a raw binary encoder.
• TIFF — Professional archival and print format. Multi-strip TIFF generated entirely in JavaScript, compatible with Adobe Photoshop, GIMP, and all print workflows.
• TGA — Targa format used in game engines and 3D software. Generated as a 32-bit uncompressed TGA with full alpha channel support.
• ICO — Windows favicon format. Multi-size ICO packing — ConvertMaster generates proper ICO headers for use in any browser or operating system.
• CUR — Windows cursor format. Uses the same multi-size ICO structure with cursor-specific header fields.
• SVG — Raster image wrapped in an SVG container. Useful for embedding images in vector workflows.
• PDF — Your image is page-fitted and exported as a PDF document using the jsPDF library, sized precisely to your image dimensions.
• PSD, EXR, HDR, DDS, JP2, JXL, HEIC — Professional and advanced outputs via the ImageMagick WASM engine. These load once (~10–20 MB), are cached by your browser, and run entirely offline after that.

How to Use ConvertMaster — Step by Step

1. Load your images: Drag and drop one or multiple image files onto the upload area, or click “Browse Files” to pick them from your device. ConvertMaster accepts all 30+ supported formats in a single batch.
2. Add more images (optional): After your initial upload, use the “+ Add More” button to add additional files to the queue without losing your existing uploads.
3. Crop or edit (optional): Hover over any image thumbnail and click “Crop & Edit” to open the crop editor. Set a free crop, fixed ratio (1:1, 4:5, 16:9), circle mask, or rounded crop. Use rotate and flip controls, then click “Save Edits.” Your original file is untouched — the edit is stored as a non-destructive override.
4. Choose your output format: Use the Output Format selector on the right panel. A format hint will appear describing the best use case for your choice.
5. Set resize dimensions (optional): Enter a target width, height, or both — with aspect ratio lock enabled by default. Use Quick Scale buttons (25%, 50%, 75%, 200%) for proportional scaling, or pick a Social Preset (Instagram, YouTube, Facebook, Full HD) to match a platform requirement exactly.
6. Set output quality: Drag the Quality slider for lossy formats (JPG, WEBP, AVIF). 90% is the recommended default balancing quality and file size.
7. Apply background color (optional): Enable “Apply background” and choose a fill color to replace transparent areas before exporting to a format that does not support transparency, such as JPG or BMP.
8. Process & Download: Click “Process & Download All (ZIP).” ConvertMaster converts every image in the queue with your settings and packages them all into a single ZIP archive downloaded to your device. Individual files can also be downloaded one at a time using the download button on each preview card.

Technical Reference

• Pure JavaScript Engine (Tier 1) — Handles JPG, PNG, WEBP, AVIF, GIF, BMP, TIFF, TGA, ICO, CUR, SVG, and PDF using hand-written binary encoders and the browser’s native canvas.toBlob() API. Zero dependencies, zero network calls, instant processing.
• ImageMagick WASM Engine (Tier 2) — Powered by ImageMagick compiled to WebAssembly via the magick-wasm project. Handles PSD, EXR, HDR, DDS, JP2, JXL, HEIC, and RAW format reading. Loads once from the CDN (~10–20 MB), is then cached by your browser’s service worker, and runs entirely offline on all subsequent sessions.
• heic2any — A JavaScript fallback library for HEIC/HEIF decoding in browsers where the WASM engine is unavailable. Provides seamless Apple HEIC support across all platforms.
• Cropper.js — An open-source, zero-dependency image cropping library that powers the Crop & Edit modal. Provides GPU-accelerated crop handles, rotation, and flip transforms.
• JSZip — Client-side ZIP file generation library. All batch-converted images are packaged into a ZIP archive entirely in memory without any server involvement.
• jsPDF — PDF generation library used for image-to-PDF conversion. Images are rendered to a canvas, then embedded into a properly-dimensioned PDF page.
• WebAssembly (Wasm) — Binary instruction format enabling near-native performance of compiled C/C++ code (ImageMagick) inside the browser sandbox. Provides the same decoding capability as desktop software, inside a browser tab.
• HTML5 Canvas API — Used for all image rendering, pixel manipulation, resize operations, background fill, and encoding. The primary drawing surface that bridges input decoding and output encoding.

ConvertMaster vs. The Competition — A Detailed Breakdown

Most people converting images online today face the same trade-offs: cloud services with upload limits and privacy risks, or heavyweight desktop software that takes minutes to load. ConvertMaster was built specifically to eliminate every one of those compromises.

vs. Cloud Converters (Convertio, CloudConvert, Squoosh)

These services process your files on their own servers. That means uploading your images — including your personal photos, client files, and confidential documents — to a machine you don’t control, waiting in a server queue, and then downloading the result. Most enforce file size caps on free tiers (typically 100 MB per day) and require paid subscriptions for batch processing or advanced formats.

ConvertMaster eliminates every one of those bottlenecks. Your images load in under a second, there is no upload wait, batch processing is built in, and no file ever leaves your device. A folder of 50 RAW files from your camera can be batch-converted to WEBP in a single operation, with no subscription, no daily cap, and no data exposure.

vs. Adobe Photoshop / Lightroom

Photoshop and Lightroom are the gold standard for professional image work, but they cost $9.99–$54.99/month, require installation on a specific machine, and take 30–90 seconds just to launch. ConvertMaster handles the most common image conversion and resizing tasks — including reading PSD, EXR, and RAW files — in a browser tab that opens instantly, on any computer, for free.

vs. GIMP

GIMP is a powerful free alternative to Photoshop, but it is a 250+ MB desktop installation that requires learning a complex interface for tasks as simple as converting a folder of images to WEBP. ConvertMaster requires no installation, no learning curve, and handles batch conversion in one click from the browser.

vs. Windows Paint / Preview (macOS)

Native OS image viewers can open and save a few formats, but they offer no batch processing, no format conversion to AVIF or WEBP, no RAW reading, and no professional format support. They work for a single image at a time. ConvertMaster handles unlimited images in a single session across 30+ formats.

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Best Mobile Image Converter — ConvertMaster vs. Phone Apps

Most people reach for their phone the moment they need to quickly resize a photo for Instagram, convert a screenshot, or turn a HEIC from their camera roll into a shareable JPEG. The problem is that every major mobile image converter app comes with trade-offs: ads, watermarks, subscriptions, upload limits, or privacy concerns. ConvertMaster runs in any mobile browser — Chrome on Android, Safari on iPhone — with the full feature set of the desktop version.

vs. Photo Converter App (Android / iOS)

Generic “Photo Converter” apps on the Play Store and App Store typically support 8–12 formats, show interstitial ads between every conversion, require in-app purchases to remove watermarks, and process files by uploading them to a remote server. On a slow mobile data connection, converting a 10 MB RAW photo through one of these apps can take over a minute. ConvertMaster works entirely offline in your mobile browser after the initial page load — no ads, no watermarks, no upload wait.

vs. Snapseed / Lightroom Mobile

These are excellent editing apps, but they are not format converters — you cannot export a HEIC as a TIFF, convert a batch of RAW files to WEBP, or generate a multi-size ICO file from a PNG. They are designed for photo editing and basic sharing exports. ConvertMaster fills the gap they don’t: pure format conversion and resizing across 30+ formats, with batch processing, from a browser tab.

vs. Files by Google / iPhone Files App

The native file manager apps on both major mobile platforms can preview many image types but offer essentially zero conversion capability. There is no “save as WEBP” or “export as PDF” option built into either. ConvertMaster turns any mobile browser into a full-featured image conversion studio accessible from the Files app’s “Open in Browser” function.

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How ConvertMaster Is Built — Architecture Overview

ConvertMaster follows a layered processing model that separates concerns between format decoding, image manipulation, and format encoding. At the outermost layer sits a browser-native drag-and-drop file intake system that normalises any input file into a displayable preview URL before passing it downstream. The manipulation layer handles all geometric transforms — resize, scale, crop, rotate, flip — on an HTML5 Canvas surface that acts as a universal pixel buffer, decoupled entirely from the input and output codec layers.

Encoding is handled by two interchangeable codec backends that are selected at runtime based on the requested output format. Standard formats are dispatched to lightweight hand-written encoders that write binary file structures — TIFF strip layout, BMP BITMAPINFOHEADER, GIF LZW compression tables, ICO directory headers — directly into ArrayBuffer memory without any third-party encoding libraries. Complex professional formats route through a WebAssembly port of a mature open-source image processing library, which is initialised asynchronously on first use and communicates with the JavaScript layer via typed array byte transfer.

Batch processing is implemented as a sequential async iterator over the image queue, with per-item progress reporting fed back to the UI through direct DOM updates. Completed encoded blobs are accumulated in a JSZip in-memory archive and flushed to a Blob URL for download only after all items complete. The crop editor integrates as a modal overlay that stores edits as data URL overrides on the file queue objects — the original File references are preserved intact until the final export pass.

The entire application is a single self-contained HTML file with no build system, no module bundler, and no server component. All external dependencies are loaded from CDN on first use and rely on standard browser caching for subsequent offline availability. This architecture means the tool can be saved locally, hosted on any static file server, or embedded in any web page without modification.

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Frequently Asked Questions

Is ConvertMaster completely free?

Yes — 100% free, permanently. This free image converter has no subscription, no watermarks on output files, no account requirement, and no daily file limit. It is a fully client-side WebAssembly and JavaScript application — the same technology stack used by professional desktop software, running directly inside your browser tab.

Privacy & Security — Do my images get uploaded anywhere?

No. ConvertMaster is a fully local image converter. Your files are loaded into your own computer’s RAM and are never transmitted over any network connection. Unlike cloud-based services that log IP addresses, retain uploaded files on their servers for hours, and are subject to data breach risks, ConvertMaster provides the same privacy guarantee as desktop software. Personal photos, medical images, legal documents, and confidential business graphics can all be processed with complete confidence. No account is ever created, no data is ever stored.

What is the difference between the Pure JS Engine and the WASM Engine?

ConvertMaster uses two processing tiers. The Pure JavaScript Engine handles standard formats (JPG, PNG, WEBP, GIF, BMP, TIFF, ICO, TGA, SVG, PDF) — these run instantly with zero loading time because they use the browser’s built-in canvas API and custom binary encoders. The ImageMagick WASM Engine handles advanced professional formats (PSD, EXR, HDR, JXL, HEIC, DDS, JP2, and all RAW formats). This engine downloads once from the CDN (approximately 10–20 MB) on first use, and is then permanently cached in your browser. After that first load, it runs entirely offline.

Why does AVIF sometimes fail to export?

AVIF export relies on your browser’s native canvas.toBlob('image/avif') support. This works in Chrome and all Chromium-based browsers (Edge, Brave, Opera). Firefox and Safari have not yet implemented this specific canvas encoding API. If AVIF export fails in your browser, switch to WEBP — it offers near-identical compression efficiency with near-universal browser support.

How does the Crop & Edit tool work?

Cropping is applied non-destructively — your original uploaded file is never modified. When you open the Crop & Edit modal for an image, make your adjustments (free crop, ratio crop, circle mask, rotate, flip), and click “Save Edits,” the edited version is stored as an override in memory. The preview thumbnail updates to show the edited version. You can re-edit any image at any time before processing. Only when you click “Process & Download All” is the edited version used for the final export.

Can I convert multiple images at once?

Yes. Upload as many images as you need — you can even add more files after your initial upload using the “+ Add More” button. All conversion settings (format, quality, resize dimensions, background color) apply uniformly to every image in the queue. Click “Process & Download All (ZIP)” to convert every image in a single batch pass and download them in one ZIP archive.

Is there a file size limit?

There is a 40 MB per-file limit enforced in the browser to prevent RAM exhaustion on lower-end devices. For files larger than 40 MB, consider splitting the batch into smaller groups. There is no overall session limit — you can process as many images as your device’s RAM can handle.

Can I use the converted files commercially?

Yes. ConvertMaster applies no watermarks and asserts no rights over your converted files. The converted images are entirely yours for any personal or commercial use. The underlying libraries (ImageMagick, Cropper.js, JSZip, jsPDF) are all open-source and permissively licensed.

Does ConvertMaster work offline?

The Pure JavaScript Engine works offline immediately — it has no external dependencies. The ImageMagick WASM engine requires an internet connection on first load to download and cache the WASM binary (~10–20 MB). After that first session, the WASM engine is cached by your browser and all formats work offline indefinitely.

Explore more tools in our Image & Design Tools collection, or return to the AIToolboxBD homepage to explore our complete directory of free browser-based utilities.