Image Compressor - Compress PNG, JPG & WEBP Images Online

Why Image Compression Matters for Your Website

Images are typically the largest files on any webpage. A single uncompressed photograph straight from a phone or camera can weigh 3-6 MB and most websites display dozens of images per page. That file weight is paid for every time a visitor loads your page, and it adds up fast.

Google has used page speed as a ranking signal since 2010. Since 2021, it is measured directly through Core Web Vitals, specifically Largest Contentful Paint (LCP), which measures how quickly the largest visible element on a page loads. For most websites, that element is an image. An uncompressed hero image or product photo can fail LCP, especially on slower mobile connections. A properly compressed version is far more likely to pass.

Beyond rankings, page speed directly affects how visitors behave on your site. Slow-loading pages increase bounce rate, reduce time on site, and cost conversions, all of which compound over time into lost revenue and lower organic visibility.

Compressing images before upload is one of the fastest and highest-impact technical SEO fixes available to most website owners. No developer, no code changes, no server configuration required. Upload the optimized file instead of the original, and the page gets lighter straight away. The tool above makes this process take seconds, here is everything you need to know to use it effectively.

How to Use the SEO Site Checker Image Compressor

The tool is completely free and works without an account. Here is the full process from upload to download:

Step 1: Upload your image. Drag and drop your image file directly onto the upload area, or click Select a File to browse your device and choose the image you want to compress. Supported formats are PNG, JPEG, JPG, and WebP. The maximum file size is 10 MB per image for guest users and 50 MB per image for logged-in users.

Step 2: Compress your image. Click the Compress Images button. The tool processes your file automatically, with no quality slider to set. It re-compresses each image for its file type and keeps the result only when it is smaller than your original, otherwise you get your original file back. To change the format as well, switch on Convert my images automatically above the upload area and pick AVIF, WEBP, JPEG or PNG. Converted files are always saved in the format you chose, even when that makes them larger.

Step 3: Review your results. A results table appears showing your file name, the original file size, the compressed file size, and the percentage reduction achieved. A higher percentage means more file size was saved. Occasionally a result will show 0% or a negative percentage, this is not an error. See the FAQ below for a full explanation of what this means.

Step 4: Download your optimised image. Click Download to save your compressed image to your device. The file is ready to upload directly to your website, CMS, social media platform, or e-commerce store.

Upload limits: Guest users (no account required) can compress up to 10 images per upload, up to 10 MB per file. Creating a free SEO Site Checker account, no credit card, no cost, raises the limit to 50 images per upload, up to 50 MB per file.

Supported Image Formats: What You Can Compress

The compressor accepts three formats (PNG, JPEG and WebP) that cover the vast majority of images used on websites, social media, and e-commerce stores. Here is what to know about each.

Compress PNG Images

PNG files use lossless compression natively, which preserves every pixel of image data but at a larger file size cost. PNGs are the standard format for logos, screenshots, icons, interface graphics, and any image that requires a transparent background. Our compressor can reduce PNG file sizes substantially while keeping transparency, although photographic PNGs often shrink much less. To do that it usually reduces the number of colors in the image (and falls back to a lossless re-save when that would look too different or would not save space), which is rarely noticeable on logos and screenshots but can show as banding in smooth gradients, so check photographic PNGs before you publish them. Compressing a PNG before uploading it to your site, especially for logos and featured graphics, is one of the easiest wins for page speed improvement. If you need to switch formats entirely, the free PNG to JPG converter handles that in one step.

Compress JPEG / JPG Images

JPEG, saved as either .jpeg or .jpg, they are the same format, is the most common format for photographs, blog featured images, editorial content, and product photos. JPEG already applies lossy compression internally, but images exported from cameras, phones, and editing software are typically saved at maximum quality settings, far higher than needed for screen display at web dimensions. Compressing a high-quality JPEG, such as a camera or phone export, often achieves 40-80% file size reductions with little visible difference at normal viewing sizes, while a JPEG that was already saved at a web-friendly quality may shrink much less. A 4 MB camera photo can often lose more than half its weight, and resizing it to its display dimensions first saves far more. If you need to convert a JPEG to PNG, the free JPG to PNG converter is available on SEO Site Checker.

Compress WebP Images

WebP is Google's modern image format, designed from the ground up for web performance. In its own published comparisons, Google reports lossy WebP files about 25-34% smaller than equivalent JPEGs and lossless WebP files about 26% smaller than equivalent PNGs. WebP is increasingly common in exports from CMS platforms, design tools, and web apps, and is the recommended format for most web images going forward. If you are already working with WebP files, the compressor accepts them and can usually reduce them further, although the file is re-encoded as lossy WebP, so a small quality loss is possible.

Lossy vs Lossless Compression: What's the Difference?

If you have used image tools before, you have likely encountered these two terms. Understanding the difference helps you make the right decision for each type of image you work with.

Lossy compression permanently removes some image data to achieve a smaller file. The data removed is typically imperceptible to the human eye at normal viewing sizes, micro-detail in backgrounds, subtle colour gradients, invisible texture in flat areas. The trade-off is that the change is irreversible: you cannot restore the original data from a lossy-compressed file. JPEG is the most widely used lossy format. Lossy compression is the right choice for: photographs, blog images, social media content, product photos, and any image where the goal is fast loading over pixel-perfect precision.

Lossless compression reduces file size by repacking image data more efficiently, without discarding any information. The image is pixel-for-pixel identical to the original after compression. File size savings are typically smaller than lossy, but quality is fully preserved. PNG is the standard lossless format. Lossless compression is the right choice for: logos, icons, screenshots, text-heavy graphics, UI elements, and any image where sharp edges and exact colour reproduction matter.

WebP is the most versatile option, it supports both lossy and lossless modes within the same format, making it ideal for modern web publishing where you want small files without choosing between quality and speed.

What does the SEO Site Checker compressor use? The tool applies optimised compression automatically based on your file type. You do not need to choose a method manually. For JPEG files it applies lossy compression: it tries four quality settings, from 82 down to 60, and keeps the smallest result, which is usually the lowest one, about quality 60. WebP files are re-encoded as lossy WebP. For PNG files it usually reduces the number of colors, which is also a lossy step, and falls back to lossless optimization when that would look too different or would not save space. Some detail can therefore be discarded in every format, and the tool does not measure visual quality for you. If you are unsure which result looks right, compare your original and compressed file at 100% zoom before publishing.

How Image Compression Directly Improves Your SEO

The connection between image file size and search rankings runs through page speed, and you can measure it.

Core Web Vitals and Largest Contentful Paint (LCP). Google's Core Web Vitals are a set of speed metrics used as ranking signals. The most impactful for image-heavy sites is LCP, the time it takes for the largest visible element on the page to fully load. For most websites, that element is a hero image, a featured image, or a product photo. Google's benchmark for a good LCP score is under 2.5 seconds. A single uncompressed 4 MB image on a standard connection can blow past that threshold on its own, especially on a mobile connection. A much lighter image, ideally resized and compressed, gives the page a far better chance of staying within range. You can measure your page's LCP score before and after compression using Google PageSpeed Insights, the improvement is often visible straight away.

Crawl budget. Googlebot allocates a finite crawl budget to each website, a limit on how many pages and resources it will process in a given crawl session. Large image files can slow down crawling, which matters most on very large sites with many thousands of pages. Compressed images can help Googlebot fetch your pages faster, although crawl budget is rarely a problem for small and mid-sized sites.

Bounce rate and user experience. Page speed and user experience are intertwined. A visitor who arrives on a slow-loading page and leaves before it finishes loading is a negative engagement signal. Image compression is one of the highest-impact, lowest-effort fixes for most slow websites, no code changes, no server upgrades, no developer required. You compress the file, you upload the compressed version, the page is faster. Run a full website SEO audit to identify technical issues affecting your site's rankings, including image formats, image caching and image metadata.

Mobile-first indexing. Google has used mobile-first indexing since 2019, meaning it primarily uses the mobile version of your pages for indexing and ranking. Mobile connections are typically slower than desktop, the impact of uncompressed images is amplified on mobile. A 3 MB product image that loads quickly on fiber can take several seconds on a weak mobile connection. Compressing images before upload is one of the most practical steps toward mobile performance improvement for most websites.

Image Compression Best Practices for Websites, Social Media and E-commerce

Compression is only one part of a complete image optimisation workflow. Here is what to do before, during, and after compression for each major use case.

Best Practices for Website and Blog Owners

A common image mistake on blogs and content sites is uploading raw files directly from a camera, phone, or design tool without any optimisation. A single unoptimised featured image can add 3-10 MB to a page that should weigh under 1 MB in total.

Compress every image before uploading, without exception. For blog featured images, aim for under 150 KB. For inline content images, target under 100 KB where possible. For full-width hero images, under 300 KB is a practical ceiling for most connection speeds.

Before compressing, also check your image dimensions. There is no benefit to uploading a 4,000px wide image if your blog column is 800px wide, the browser downloads the full 4,000px file and scales it down visually. Resize your images to the display dimensions before compressing for the maximum file size reduction.

Name your image files descriptively before uploading. Search engines read file names as a relevance signal,free-seo-tools-dashboard.jpg communicates content context; IMG_4872.jpg communicates nothing. Compression does not affect file names, so rename files before running them through the compressor. Finally, add alt text after uploading to every image, this is essential for accessibility and a confirmed on-page SEO signal.

Best Practices for Social Media

Most major social platforms, including Facebook, Instagram, LinkedIn, Pinterest and X, recompress uploaded images through their own processing pipelines. This second round of compression is applied on top of whatever quality your original file had. If your original was already large and uncompressed, the platform's recompression can produce noticeably degraded results: blurry edges, colour shifts, and visible artefacts that make professional images look amateur.

Starting with an already-compressed file means the platform's automatic recompression has less work to do and may introduce less visible degradation. Compress to JPEG for social uploads, WebP is not universally accepted across social platforms and scheduling tools, and JPEG gives you a small file with the widest compatibility.

Target file sizes before uploading: Facebook and LinkedIn feed images under 1 MB, Instagram feed images under 500 KB, Pinterest pins under 500 KB. Compressing to these levels before upload gives you the best chance of the platform preserving your image quality through its own processing.

Best Practices for E-commerce Stores

Product images are among the most viewed and most numerous images on an e-commerce site. They are also often unoptimized, store owners upload product photography straight from the camera or photographer's delivery, without any compression step. On a store with 200 products and 5 images per product, that is 1,000 unoptimised images adding unnecessary weight to every product page load.

Many e-commerce platforms do not automatically compress uploaded images to optimal levels, so compressing them yourself before upload is a sensible habit. Compress all product images to under 200 KB before uploading. Hero and banner images should be under 300 KB. Background images and category header graphics should be under 150 KB.

Consistent image dimensions across your product catalogue also improve perceived page load consistency. When all product images are the same dimensions and similar file sizes, pages load evenly rather than progressively, which reduces the visual jank that pushes bounce rates up on slow connections. For small business websites running e-commerce, image optimisation is typically one of the fastest paths to a measurable improvement in page speed scores.

How Much Can You Compress an Image Without Losing Quality?

For most web-use images, the answer is: significantly more than people expect.

Photographs exported from cameras, phones, and editing software are typically saved at maximum quality, often 90-100% JPEG quality, because storage is cheap and the software defaults to preserving everything. But on screen, most people cannot see the difference between 90% and 75% JPEG quality at normal viewing distances. Compressing a camera JPEG to 75-80% quality is usually hard to tell apart at screen size and typically produces files 50-70% smaller. This tool goes lower for JPEG files, to about quality 60, so check its output at full size.

PNG files saved from Photoshop, Figma, or Illustrator often contain extensive metadata, embedded colour profiles, thumbnail previews, creation software information, GPS data, that adds file size with zero visual benefit. Stripping this metadata can noticeably reduce PNG file sizes, usually with no visible change to how the image appears.

The practical ceiling for most web images: you can often compress to 40-60% of the original file size with little visible difference. Compressing aggressively beyond that, particularly with JPEG files, starts to introduce visible artefacts: blockiness in flat colour areas, colour banding in gradients, halos around high-contrast edges like text on images. These are the signs you have gone too far.

If the results table shows a very small percentage reduction, under 5%, the image was already compressed close to the smallest size this tool can reach. When the tool cannot make a file smaller it returns your original, with a small amount of tool metadata added, so the figure can read slightly below zero. A larger negative figure appears when you convert to a format that is heavier than the original, for example JPG to PNG.

More Free Image and SEO Tools

After compressing your images, the next step for most users is getting them the right dimensions. Use the free Image Resizer to resize an image by percentage or to the pixel dimensions you choose (it only makes images smaller, never larger) before or after compression. To convert between formats, the PNG to JPG Converter and JPG to PNG Converter handle format switching in one step. If you need a favicon for your website, the free Favicon Generator creates a favicon.ico, PNG icons for browsers, iOS and Android, a web manifest and the HTML snippet from a single image upload. To check how your site's image performance is affecting your overall SEO score, run a free website SEO audit, it checks image formats, caching and metadata alongside the other on-page factors.