# ImageTool.app — full content > ImageTool.app offers free online image compression with lossless support for JPG, PNG, GIF and SVG. Everything runs locally — no upload required. All content below is the English version. The same pages exist in 17 languages under a URL prefix (zh, zh-Hant, en, ja, ko, de, fr, es, it, pt-BR, nl, pl, ru, sv, da, tr, vi). --- ## Online image compression ### PNG compression — https://imagetool.app/en/compress/png *Smaller PNGs, faster loads* Unoptimized PNGs are often 1–2x larger than they need to be. ImgZilla analyzes the palette structure locally in your browser, removes redundant metadata and applies smart quantization to shrink file size dramatically while fully preserving transparent pixels — images are never uploaded to any server. **Lossless PNG compression** - **Alpha channel always protected**: Transparent PNGs are easily wrecked by poor compressors. We make alpha handling the top priority, so transparent areas stay pristine. - **Palette optimization, no banding**: PNG8 quantization tends to band on gradients. We use perceptual quantization to trim the palette almost imperceptibly while keeping visible detail. - **Batch-compress PNG folders**: The desktop app compresses an entire Figma / Sketch export directory at once — dozens of icons in seconds. - **Built for Core Web Vitals**: Google's LCP penalizes oversized images. Compressed PNGs load 3–5x faster, directly improving your Lighthouse score. **How to compress PNG** 1. **Drop in a PNG**: Works with logos, UI screenshots, icons, product shots and Figma / Sketch exports — transparency detected automatically. 2. **Download the PNG**: Format and transparency unchanged, file size much smaller — no format conversion needed. #### PNG FAQ ##### Will compression break a transparent PNG? No. ImgZilla specifically protects the alpha channel data throughout compression, so transparency is always preserved. ##### How small can a PNG get? Logos and icons typically shrink 10–20%, screenshots and photos often 20–30%, depending on image complexity. ##### Should photos be PNG or JPG? Photos are better as JPG. PNG is best for images with transparency, text, sharp edges or large flat color areas. ##### Can I compress PNG without quality loss? Yes. Lossless compression only removes metadata and optimizes file structure, with zero quality loss. ### JPG compression — https://imagetool.app/en/compress/jpg *Offline local lossless compression — images processed on your device, no upload.* Unlike online tools that upload your files to third-party servers, ImgZilla compresses JPG fast and entirely locally, with virtually no quality loss. 100% local, no signup, no subscription. **Why local JPG compression** - **Faster batches**: Compress JPG quickly even on an ordinary computer — no upload waits, server queues or rate limits. - **Zero upload, more privacy**: Files always stay local, never uploaded to any third-party server — client material and private photos stay safe. - **No file size limit**: Easily handle tens-of-MB shots from wedding proofs or medium-format cameras, free of the size caps online tools usually impose. - **Quality stays sharp**: A perceptual visual compression algorithm keeps sharp edges and only compresses flat areas aggressively — the difference is barely visible. **How to compress JPG** 1. **Drop in a JPG**: Just drag your JPG in — no upload. 2. **Export**: Export right after compression — no ZIP packaging, no waiting on a server. #### JPG FAQ ##### Will quality drop noticeably after compression? The before/after difference is nearly imperceptible, typically shrinking 50–80% (e.g. 4MB down to 800KB–1.2MB). ##### Will my images be uploaded? No. Compression happens entirely locally; your images never leave your device. ##### What's the difference between JPG and JPEG? They're exactly the same format, just different file extensions, stemming from early Windows limits on extension length. ##### Can I batch-compress? The online tool is great for a few images quickly; the desktop app supports unlimited batches and multi-threaded whole-folder compression. ### JPEG compression — https://imagetool.app/en/compress/jpeg *Offline local lossless compression — images processed on your device, no upload.* Unlike online tools that upload your files to third-party servers, ImgZilla compresses JPEG fast and entirely locally, with virtually no quality loss. 100% local, no signup, no subscription. **Why local JPEG compression** - **Faster batches**: Compress JPEG quickly even on an ordinary computer — no upload waits, server queues or rate limits. - **Zero upload, more privacy**: Files always stay local, never uploaded to any third-party server — client material and private photos stay safe. - **No file size limit**: Easily handle tens-of-MB shots from wedding proofs or medium-format cameras, free of the size caps online tools usually impose. - **Quality stays sharp**: A perceptual visual compression algorithm keeps sharp edges and only compresses flat areas aggressively — the difference is barely visible. **How to compress JPEG** 1. **Drop in a JPEG**: Just drag your JPEG in — no upload. 2. **Export**: Export right after compression — no ZIP packaging, no waiting on a server. #### JPEG FAQ ##### Will quality drop noticeably after compression? The before/after difference is nearly imperceptible, typically shrinking 50–80% (e.g. 4MB down to 800KB–1.2MB). ##### Will my images be uploaded? No. Compression happens entirely locally; your images never leave your device. ##### What's the difference between JPG and JPEG? They're exactly the same format, just different file extensions, stemming from early Windows limits on extension length. ##### Can I batch-compress? The online tool is great for a few images quickly; the desktop app supports unlimited batches and multi-threaded whole-folder compression. ### SVG compression — https://imagetool.app/en/compress/svg *Smaller SVGs, just as crisp* SVG is essentially text code, and design tools often export SVGs bloated with redundancy — editor comments, extra metadata, excessive coordinate precision and hidden layers. ImgZilla trims this redundant code locally to shrink size without affecting how it renders — files are never uploaded to any server. **Why SVG compression is different** - **Vectors never blur**: SVG is vector graphics — crisp at any scale. Compression only trims code, never sacrifices quality. - **Clean up redundant code**: Automatically removes editor comments, useless metadata, empty groups and hidden elements for a cleaner, lighter file. - **Trim path precision**: Reins in excessive coordinate decimals to a sensible range, noticeably shortening path data with no visible difference. - **Better for inline and web**: Smaller SVGs inline into HTML without bloat, load faster and help your Core Web Vitals. **How to compress SVG** 1. **Drop in an SVG**: Works with icons and illustrations exported from Figma, Sketch, Illustrator and more. 2. **Export the SVG**: Still standard SVG, renders identically, but with leaner code and a smaller file. #### SVG FAQ ##### Will compression change how the SVG looks? No. Optimization only removes redundant code and trims precision; the rendered graphic stays visually identical to the original. ##### How small can an SVG get? Design-tool exports typically shrink 10–30%, depending on the redundant data and path complexity. ##### Will it break animation or interactivity in the SVG? The default cleanup preserves necessary ids, classes and animation structure; if in doubt, you can re-verify after compression. ##### How is it different from compressing JPG or PNG? SVG is vector text, so it compresses code rather than pixels — the result is lossless and infinitely scalable, whereas bitmap compression targets pixel data. ### GIF compression — https://imagetool.app/en/compress/gif *GIFs that open instantly, animation still smooth* A 5-second UI demo or a social reaction GIF can easily be 8–15MB — too big for email, Slack or web embeds. ImgZilla compresses GIFs with frame differencing, palette reduction and lossless animation optimization, entirely locally, no upload. **How we compress GIF** - **Frame differencing**: Stores only what changes between frames rather than each full frame, cutting size dramatically for static backgrounds or slow motion. - **Palette optimization**: Perceptual color selection picks the 256 colors the eye is most sensitive to, trimming the palette with no visible banding. - **Dither control**: From Floyd–Steinberg dithering for gradients to no dithering for flat-color animations — pick what fits. - **Batch processing**: The desktop app compresses an entire GIF library at once — email campaigns, product docs, social assets — in seconds. **How to compress GIF** 1. **Drop in a GIF**: Just drag your animated GIF in — no upload. 2. **Export the GIF**: Same duration and frame count, noticeably smaller file. #### GIF FAQ ##### Why are GIFs so large? Every frame is a full image with its own palette. A 3-second, 15fps animation is 45 frames — size adds up fast without optimization. ##### Will compression break the animation? No. Optimization only targets data redundancy and color efficiency; duration, frame count and look are all preserved. ##### Can GIFs with transparent backgrounds be compressed? Yes. A GIF's binary transparency is fully preserved throughout compression. --- ## About ImgZilla — https://imagetool.app/en/faq ### Will my images be uploaded? No. ImgZilla compresses entirely on your Mac, no network needed — your image data is never uploaded to any cloud. ### Will quality drop after compression? Built-in deep optimization tuned per format compresses heavily while keeping images sharp, averaging over 50% and up to 90%+. You can also use the built-in compare tool to see the before/after difference. ### Could my originals be overwritten or lost? With original backup enabled, the original is automatically saved to the Trash before compression and can be recovered anytime. (Note: for disks that don't support the Trash, you'll be prompted to set a backup folder.) ### Which formats are supported? JPG, PNG, GIF, SVG, HEIC/HEIF, WebP, AVIF and other mainstream image formats. ### How much does it cost? There's a free daily allowance; for heavier use you can choose a one-time purchase or a subscription to fit your needs. --- ## ImgZilla User Guide — https://imagetool.app/en/imgzilla/docs ### 1. Getting Started #### Which formats can ImgZilla compress? Eight formats are supported: **JPG / JPEG, PNG, GIF, SVG, HEIC / HEIF, WebP, AVIF**. Files in other formats (along with hidden files and directories whose names start with .) are skipped automatically when you add them. #### How do I add images? Two ways, with identical results: - **Drag and drop**: drag files or folders straight into the window. - **Click to choose**: click the logo area in the middle of the window and pick files or folders in the panel that opens. When you drop a folder, ImgZilla searches it recursively for images (directories nested more than 20 levels deep are skipped with a notice). Duplicate files are only added once. If your selection contains no supported images at all, a message tells you which formats are supported. #### I have a lot of files and scanning is slow. What can I do? The bottom bar shows "Finding images" along with a "Cancel" button. Click it to stop the scan — the files already found stay in the list. #### How do I start compressing? Once your list is ready, click **Start Compression** in the bottom-right corner. Images are processed one by one in order, and the item currently being compressed scrolls into view automatically. - While compression runs, the button becomes **Stop Compression** — click it to abort at any time. - When everything is done you get a system notification, and the button becomes **Clear** (clears the list and returns to the start screen). - The bottom bar shows the number of files processed plus the percentage and size saved, in real time. > Hovering over the list pauses the auto-scrolling so you can read it, and a small bar floats up at the bottom showing the image currently being compressed. #### Does compression modify the original file? **Yes.** ImgZilla compresses in place: the result is written back to the original path, keeping the same file name and location. By default your originals are not lost — see the next section. ### 2. Original Safety and Backups #### Will my originals be overwritten? Can I get them back? With the default settings, **yes, you can recover them**. On a successful compression the original is first moved to the **system Trash**, and only then is the compressed result written to the original path. To restore one, just open the Trash and choose "Put Back". This behaviour is controlled by the **"Move originals to Trash"** switch in Settings, which is on by default. #### Can I turn off "Move originals to Trash"? You can, but **once it's off, compression overwrites the original file directly and the original cannot be recovered**. You'll be asked to confirm. We recommend turning it off only if you have another backup or are short on disk space. #### What does "Cannot move to Trash" mean during compression? Some locations (external disks, network volumes, or cases where the system granted access to a single file but not to its parent folder) don't allow moving files to the Trash. When this happens, compression **pauses** and a dialog asks you to choose: - **Choose a backup folder**: pick a folder; originals are copied there before being overwritten. That folder is also remembered as your default backup folder. - **Skip backup**: after a confirmation, originals are overwritten directly with **no backup kept and no way to recover them**. - **Close the dialog**: treated as a cancellation — the whole compression job is aborted. Your choice applies to **all remaining files in this run**; you won't be asked again for every image. #### Where is the default backup folder? It is created automatically on first launch at: ~/Library/Application Support/ImgZilla Backups/ Each compression session creates a new time-stamped subfolder inside it (for example 2026-07-12_14-30-05). #### Can I compare the results afterwards? Every successfully compressed image in the list has a **Compare** button on its right. Clicking it opens the image comparison window with the backed-up original on the left and the compressed result on the right. See section 4 for details. ### 3. Settings Open Settings from the menu **ImgZilla → Settings** (shortcut ⌘,), the gear icon in the bottom-right of the start screen, or the gear button next to "Start Compression" in the bottom bar. #### What is "Preserve EXIF data"? Should I enable it? It controls whether metadata inside the image (capture settings, GPS location, ICC colour profile, and so on) is kept. - **Off by default**: metadata is stripped, making files smaller and better for privacy (your shooting location isn't leaked). - **On**: metadata is preserved and files are slightly larger. Recommended for photography, or whenever you need to keep copyright or colour information. This applies to PNG, JPEG, WebP, AVIF and HEIC. #### Which languages are supported? Settings lets you switch between 19 languages: Follow System, 简体中文, 繁體中文, English, 日本語, 한국어, Français, Deutsch, Español, Italiano, Português (Brasil), Русский, Nederlands, Polski, Svenska, Dansk, Türkçe, العربية, Tiếng Việt. The interface updates immediately — no restart needed. ### 4. The Image Comparison Window #### How do I open the comparison window? Three ways: - The menu **ImgZilla → Compare Images**, shortcut ⌘D; - The compare icon in the top-right of the start screen; - The **Compare** button on any image in the list once it has finished compressing — it loads the original and the compressed version automatically (note: this button only appears when "Move originals to Trash" or a backup folder is enabled). #### How does the comparison window work? There are two slots: **the left one is "before", the right one is "after"**. You can drop an image straight into an empty slot or click to choose one; a loaded slot can be swapped via "Choose again". Once both images are loaded: - **Drag the divider** in the middle left and right to compare the same area; - **Zoom** with the + / - buttons in the toolbar, the "Actual Size" button, or your mouse wheel / trackpad pinch. The current zoom level is shown on the left of the toolbar; - **Drag the canvas** to pan. If both sides point to the same file, a note appears at the bottom of the window. ### 5. Free Quota and Purchases #### What are the limits of the free version? The free version compresses **up to 10 images per day**. Only **successful** compressions count against the quota — failures and images that are "already minimal" (can't be compressed further) don't use any. The quota resets automatically every day (it refreshes across midnight even if the app stays in the background, so no restart is needed). #### What happens when I run out of quota? The current compression job **pauses automatically** (it isn't aborted) and the purchase panel opens. After a successful purchase, the paused job **resumes automatically from where it stopped** — you don't need to add the files again. #### How do I remove the limit? Click any "Remove limit" button to open the purchase panel. You have two options: - **Lifetime**: a one-time purchase with no image limit, forever. - **Monthly subscription**. Prices are shown according to your App Store region. #### I got a new Mac or reinstalled the app — what about my earlier purchase? Click **Restore Purchases** (available in both the purchase panel and Settings). If a previous purchase is detected, your access is restored automatically; if there is nothing to restore, you'll be told so. ### 6. Results and Statuses #### What does "Already minimal" mean in the list? It means the image didn't get meaningfully smaller (**less than 0.4% reduction**). ImgZilla keeps the original file untouched and doesn't use any of your free quota. Images that have already been optimised usually end up in this state. #### What does "Compression failed" mean? The encoder couldn't process the file (it's corrupted, malformed, and so on). The original file is left unchanged and no free quota is used. Once everything finishes, a summary tells you how many failed. > By the way: ImgZilla detects each file’s **real format**, so a file named .png that is actually a JPEG still gets compressed correctly. #### What are the buttons on each list item? - **Compare**: opens the comparison window (only shown for successful compressions that have a backup); - **Reveal**: shows the file in Finder; - **Remove**: takes the image out of the compression list (the file itself is not deleted). #### What do the two lines of numbers at the bottom mean? - First line: how many files have been processed, plus the overall percentage and size saved (savings under 1 KB aren't shown); - Second line: the total number of files in the list and their total size. ### 7. Other #### What happens if I close the window mid-compression? A confirmation dialog appears ("Compression isn't finished — quit anyway?"). Choosing to quit aborts the job; images that were already compressed are unaffected. #### Are my images uploaded to a server? No. Everything is processed 100% locally, and the app needs no network connection (apart from App Store purchase validation). #### How do I report a problem? Use the menu **Help → Feedback**, which opens [imagetool.app/ImgZilla](https://imagetool.app/ImgZilla).