Truecolor or auto palette (≤256 colors) — best for UI, logos, and masters.
Never emit palette PNG even if ≤256 colors (can increase size).
Processing runs locally with UPNG.js (palette + zlib) in your tab—no image upload to SynthQuery. EXIF and ancillary chunks from the original PNG are not preserved (privacy-friendly for screenshots). For smallest photographic delivery on the web, also try the WebP Converter.
Files
Drop PNG, JPG, WebP, GIF, or BMP here
Output is always PNG · batch up to 50 files · max 45.00 MB each · quantization + zlib recompression
About this tool
The SynthQuery PNG Compressor is a free, browser-based utility that shrinks Portable Network Graphics files—or converts other common raster inputs into leaner PNG outputs—without uploading your pixels to our servers. You drag in screenshots, UI assets, marketing stills, or supplier catalogs, choose between lossless recompression with automatic palette detection and aggressive quantization presets, optionally clamp the longest edge or scale by percentage while preserving aspect ratio, and download each result with clear before-and-after byte counts so performance budgets stay defensible in stand-ups. The encoder path combines fast PNG decode, optional high-quality canvas resampling, and the widely deployed UPNG.js library for zlib-backed IDAT chunks and intelligent palette selection, which means you get credible compression signals instead of opaque “magic percent” sliders that hide what changed. Because decoding and re-encoding happen entirely inside your tab, EXIF location fields, embedded ICC sidecars, and text chunks such as iTXt or zTXt are not carried forward—an intentional default for teams redistributing user-supplied captures under privacy review. The tool belongs to our Free tools series alongside the WebP Converter, Image Resizer, HTML utilities, and counting or grammar helpers, while the complete SynthQuery catalog at /tools—linked from the site footer as “All tools” (https://synthquery.com/tools)—anchors AI detection, SynthRead readability, plagiarism scanning, humanization, and background removal when your workflow graduates from bytes to narrative quality.
What this tool does
PNG stores lossless raster data with optional alpha, filter bytes per scanline, and DEFLATE-compressed IDAT segments. Not every exporter chooses optimal filters or chunk ordering; a “lossless” pass through a modern encoder can therefore reduce bytes even when pixels look identical, especially for screenshots with large flat regions where Paeth and None filters interact efficiently with zlib. SynthQuery exposes that behavior as Lossless / auto palette: truecolor RGBA stays truecolor when gradients demand it, while images with a small unique color count can collapse into palette mode automatically for smaller files without asking you to count colors manually.
When you need smaller payloads at the cost of banding, choose one of the quantization presets (~256 down to ~32 representative colors). UPNG’s quantizer builds a reduced color set, maps each pixel to the nearest representative, and emits palette PNGs with tight bit depths when possible. Expect dithering-like patterns on smooth skies and skin tones—that is the trade for megabytes saved on long article pages. Pair quantization with responsive resizing: limiting the longest edge to 1600 or 1920 pixels often dominates byte wins for photographic PNGs that never render full width on mobile.
Resize semantics mirror our WebP Converter. Original dimensions respect the source unless safety caps prevent multi-hundred-megapixel canvases from freezing tabs. Limit longest edge proportionally scales so the larger side matches your pick—ideal for hero regions, Open Graph images, and CMS max-width rules. Scale by percent multiplies both axes equally, which is convenient when design tools exported @2× art but your breakpoint only needs 1× density. Non-PNG inputs such as JPEG, WebP, GIF, or BMP decode through the browser, rasterize to RGBA, then encode as PNG; animated GIFs and APNGs export the first frame only, with on-row badges so motion designers know to reach for video codecs separately.
Batch mode queues many files with per-row status, errors, and individual downloads. “Download all” fires staggered saves; if the browser blocks multiples, per-row buttons remain reliable. Advanced users can force truecolor RGBA even when an image could palette-collapse—useful when downstream tooling mishandles PLTE chunks or when you want predictable RGBA semantics at the cost of extra bytes. Nothing in this flow transmits your image bytes to SynthQuery’s API: network activity is the normal page load plus any remote assets your own HTML references elsewhere.
Use cases
Web performance engineers preparing a Core Web Vitals review compress oversized PNG heroes exported from Figma, compare byte deltas against originals, and attach numbers to pull requests before enabling CDN auto-optimization. E-commerce teams normalize supplier PNGs with inconsistent zlib quality, then hand results to the Image Resizer when storefront rules demand exact widths. Content marketers shrink email-safe PNG buttons and dividers after the Word Counter confirms copy length, keeping Gmail clipping thresholds farther away.
Developers documenting open-source apps compress retina screenshots for README files so clones stay quick worldwide. Support engineers strip metadata accidentally embedded in ticket attachments before posting to public forums. Accessibility advocates keep crisp iconography in lossless mode while verifying alt text with the Grammar Checker and reading level with SynthRead on surrounding copy.
Design systems that mandate PNG for transparency across Safari-heavy audiences use quantization selectively: logos stay lossless, textured marketing bands pick 128-color presets. Students learning information theory can compare palette sizes against perceptual quality without installing ImageMagick locally. Agencies bookmark this page next to the WebP Converter to choose format per channel—PNG when alpha and sharp edges matter, WebP when photographic weight matters more.
How SynthQuery compares
Hosted converters vary from single-file upload widgets backed by opaque infrastructure to desktop suites with ICC-managed print pipelines. SynthQuery targets privacy-first, explainable compression with explicit color strategies and resize semantics, nested beside AI writing and verification utilities. Use the matrix to reason about workflow fit—not to crown a universal winner, because regulated environments sometimes require air-gapped desktop tools regardless of convenience.
Aspect
SynthQuery
Typical alternatives
Privacy model
Encode locally in-browser; image bytes are not sent to SynthQuery for compression.
Many “free” sites upload to shared backends—read privacy policies before confidential screenshots.
Color control
Lossless / auto palette plus explicit quantization rungs (256→32) with honest banding trade-offs.
Often a single quality slider that obscures whether output is lossy JPEG-in-PNG or true PNG.
Resize + batch
Longest-edge clamp, percent scale, queue many files, per-row byte stats and errors.
Frequent one-at-a-time uploads without dimension tooling or batch transparency.
Animation
APNG and GIF decode to first frame with visible badges; motion requires separate video tooling.
Some tools silently flatten or corrupt frame disposal metadata—always verify motion separately.
Ecosystem
Listed on /free-tools with internal links to WebP, resizer, grammar, dictionary, and /tools hub.
Standalone utilities disconnected from editorial, detection, or plagiarism workflows.
How to use this tool effectively
Start from the highest-quality master you own—recompressing tiny, already-crushed social assets may inflate noise or waste time. Pick Lossless / auto palette when transparency edges, text-in-icon clarity, or brand color exactness matters. If file size still violates your performance budget, step down quantization gradually (256 → 128 → 64) until banding becomes unacceptable for the viewing distance and display size you care about.
Configure resize when template max-width is known: e-commerce cards at 800 px, blog figures at 1200 px, or Open Graph images at platform-specific widths. Use percent scale when swapping @2× exports for 1× breakpoints. Drag files onto the drop zone or use Add images; watch badges for GIF or APNG first-frame behavior. Press Compress / refresh all after changing settings so every row reflects the same pipeline.
Read each row’s byte arrow: original → output and percent change. Download individually for reliability, or Download all and approve multiple-save prompts if your browser asks. When photographic content tolerates lossy delivery, open the WebP Converter in another tab and compare both formats against the same master. Bookmark /free-tools for the utilities grid and use the footer link to /tools when you need the full SynthQuery product list.
Limitations and best practices
Browser-based PNG tooling is not a substitute for CMYK print RIPs, legal redaction suites, or archival TIFF workflows with embedded color profiles. Critical print jobs belong in calibrated desktop software. Quantization is irreversible—keep lossless masters in versioned storage before aggressive palette tests. Very wide panoramas may hit memory limits; split externally first.
PNG wins for sharp transparency and lossless editing chains; JPEG and WebP often win raw bytes on photographic scenes—choose per asset. Indexed color modes can surprise designers who expect continuous-tone skies; preview on both sRGB monitors and OLED phones before locking a preset. When stakeholders ask for “the smallest PNG,” clarify whether they mean smallest for identical pixels (lossless zlib tuning) or smallest acceptable visually (quantization plus resize). Accessibility still requires descriptive alt text, sufficient contrast, and avoiding text baked into images when live HTML text is viable. SEO gains come from faster LCP when images are LCP candidates, correct width/height attributes to limit CLS, and strong page copy—compression alone does not rescue thin content. Pair this utility with Grammar, SynthRead, plagiarism checks, and the AI Content Detector when publishing mixed human-and-AI articles.
Every product surface from AI detection and humanization to plagiarism, readability, background removal, and more—same destination as the footer “All tools” link at https://synthquery.com/tools.
Screen synthetic artwork before publishing alongside freshly compressed PNGs.
Frequently asked questions
Yes—the PNG Compressor is free for typical browser use, and the compression pipeline executes locally in your device using JavaScript and canvas APIs together with the UPNG.js encoder. Files you select are read into memory in your tab; SynthQuery does not receive those bytes for encoding. You may see ordinary network requests for loading the web application, analytics as configured by your deployment, or any third-party assets you intentionally embed elsewhere on your site, but not a bulk transfer of your images to a SynthQuery transcoder. That model matters for NDAs, pre-release UI captures, and regulated personal data—though stripping ancillary chunks reduces accidental metadata leaks, it does not anonymize faces or confidential text visible in the pixels. Follow your organization’s data-handling policy and keep archival masters under version control even when web copies are aggressively compressed.
Lossless / auto palette aims to preserve per-pixel fidelity: the encoder may re-filter and re-DEFLATE IDAT streams, and it can automatically emit a palette PNG when the unique color count is small enough to benefit. Quantization presets intentionally reduce the number of representative colors—roughly 256, 128, 64, or 32—so smooth gradients posterize and file sizes drop sharply. Choose lossless when transparency edges, small text inside icons, or brand-critical flat colors must stay exact. Choose quantization when you consciously trade banding for bandwidth on illustrations, textured backgrounds, or thumbnails where viewers will not inspect pixels at 100% zoom. You can step down preset strength until artifacts appear, then back up one notch; document the preset in your design system so engineers can reproduce it in server-side Sharp or ffmpeg scripts later.
Not every input benefits from another PNG generation pass. Already-optimized exports from professional tools, tiny icons with minimal zlib overhead, or noise-heavy textures can grow slightly when re-wrapped because filter heuristics and chunk choices differ between encoders. If the output grows, stay on the original file, try a milder preset, or switch formats—WebP or JPEG often wins on photographic content. Some teams automate “keep smaller of source vs optimized” per asset; you can mimic that manually by reading the byte labels in each row. Remember perceptual quality: a marginally larger PNG might still look cleaner than a heavily quantized sibling.
Resize usually dominates byte savings for oversized camera or screenshot PNGs that your layout never displays at full resolution. Set longest-edge limits aligned with real CSS widths—there is little value shipping a 6000 px wide PNG inside a 720 px column. After dimensions match delivery reality, decide whether lossless recompression clears the budget; if not, add quantization until artifacts are acceptable at the intended viewing distance. Avoid double aggressive steps in separate tools without saving a lossless intermediate when you still need editing headroom. For Retina displays, pair logical CSS widths with srcset so 2× assets exist without shipping 3× waste.
The decoder reads the first frame of animated PNG (APNG) files and GIFs, then emits a single static PNG output. Badges in the file list call this out so motion designers are not surprised. If looping motion is required, export MP4 or WebM video, use Lottie for vector motion, or run specialized animation tooling that preserves timing and disposal rules. First-frame exports are still useful for poster images, email-safe stills, or LCP placeholders while video lazy-loads.
Lighter images can improve Largest Contentful Paint when an image is the LCP element, and correct width/height attributes help Cumulative Layout Shift. Search engines reward helpful content and solid page experience signals together—not the PNG format by itself. Combine compression with meaningful alt text, logical heading hierarchy, internal links to related tools and articles, and substantive copy. Use Search Console and real-user monitoring to validate improvements. SynthQuery’s Grammar Checker, SynthRead readability analyzer, plagiarism tools, and AI detectors support the textual side of SEO once media weight is under control.
No—this utility targets sRGB-ish screen delivery through browser canvases and PNG RGBA encoders. Print pipelines that require CMYK separation, spot inks, bleed, or ICC-managed proofs should stay in desktop publishing software and calibrated review environments. If someone hands you a CMYK JPEG labeled as PNG, expect unpredictable browser decode behavior; normalize color intent outside this page before web publication.
Both tools run locally and support batch workflows with resize helpers, but they optimize for different trade-offs. PNG preserves lossless semantics and alpha edges that UI designers love; WebP often yields smaller photographic assets at comparable perceived quality using lossy compression. Many teams serve WebP (or AVIF) to modern browsers with PNG fallbacks, or choose one format per asset based on subject matter. SynthQuery links the utilities together so you can benchmark both from the same master file without leaving the Free tools ecosystem.
The canvas and UPNG pipeline do not copy EXIF geotags, camera serial fields, XMP packets, embedded ICC profiles, or ancillary text chunks from the source PNG. That is helpful before publishing screenshots that accidentally contain GPS coordinates, yet harmful if you relied on color profiles for niche display chains. Keep original masters with metadata in secure storage when you need provenance or color-critical archives. This tool optimizes redistribution copies, not legal records of a photograph.
Current Chromium, Firefox, and Edge builds handle canvas draws, file reads, and dynamic import of UPNG.js reliably. Safari generally works on recent versions; if encoding fails, update the browser or try another channel. Locked-down enterprise browsers may block module loading—use policy-approved environments. Mobile Safari often succeeds but may throttle very large batches; process fewer files per pass on constrained devices.
Free tools are lightweight utilities—PNG compression, WebP conversion, HTML preview, unit converters, counters, dictionary, grammar, and similar—designed for quick tasks without signing in. They are listed together on /free-tools. The broader /tools page is the complete SynthQuery catalog: AI detection, SynthRead readability, plagiarism scanning, humanization, paraphrasing, summarization, translation, background removal, and more advanced flows that may require accounts or credits. The site footer links to /tools (https://synthquery.com/tools) on every marketing page so you can jump from any article or landing view to the full directory without memorizing URLs. Bookmark both hubs if you alternate between daily utilities and deep content intelligence.
Treat browser presets as experiments that inform server-side automation. Note the color preset, longest-edge value, and percent scale that produced acceptable artifacts, then reproduce similar behavior with Sharp, libvips, pngquant, oxipng, or ffmpeg in CI. Automated pipelines should also compare output sizes against sources, generate responsive variants, and upload to your CDN with cache-friendly filenames. SynthQuery’s API documentation describes separate server-side capabilities; this free page remains a human-friendly sandbox rather than a batch worker for million-file archives.