Compress Image Online Free: Reduce Image File Size Without Quality Loss

Compress your images for free online

PDFSpot's Image Compressor reduces JPG and PNG file sizes by up to 80% while preserving visual quality. No software, no account.

1. 1Go to the Image Compressor tool above.
2. 2Upload your JPG or PNG image.
3. 3Choose a quality level — 85% is the sweet spot for most images.
4. 4Click Compress and download your optimised image.
5. 5The tool shows you the exact reduction in file size.

Why image file size matters

Large images have real costs:

Website speed — Images are typically the largest assets on a webpage. Google PageSpeed and Core Web Vitals penalise slow-loading images. A 1MB image taking 3 seconds to load costs you search rankings and user patience.

Email limits — Most email providers cap attachments at 10–25MB. A single high-resolution photo from a modern camera can be 5–10MB — compress before attaching.

Storage — Hundreds of uncompressed photos accumulate quickly. Compressing archives saves gigabytes over time.

Upload limits — Social media platforms, job application portals, and web forms often have file size caps. Compression gets your image under the limit without resizing.

Lossy vs lossless compression: what's the difference?

Lossy compression (used for JPG) permanently removes some image data to reduce the file size. At quality settings of 80–90%, the visual difference is imperceptible — but you cannot recover the lost data. Never repeatedly re-compress the same JPG (quality degrades each time). Always keep the original.

Lossless compression (used for PNG, GIF) reduces the file size by optimising how the data is stored, without discarding any information. The output is identical to the input — every pixel is preserved. PNG files are typically 20–40% smaller after lossless compression.

What quality setting should I use?

Here is a practical guide:

95% quality — Near-original quality, very small size reduction. Use for professional print or archiving.

85% quality — Recommended for most uses. Excellent visual quality with significant file size savings. Hard to tell from the original.

75% quality — Good quality, smaller file. Suitable for social media, blogs, and web use.

60% quality — Noticeable quality reduction at close inspection. Use only where file size is critical (email, slow connections).

40% quality — Visibly degraded. Use only for thumbnails or previews.

How to optimise images for the web

Good web image optimisation combines compression with correct sizing and format choice:

• ✓Resize images to the actual display dimensions before compressing — a 4000px image displayed at 800px is wasting bandwidth.
• ✓Use JPG for photographs and images with many colours.
• ✓Use PNG for screenshots, graphics, logos, and images with transparency.
• ✓Use WebP if your platform supports it — it is 25–35% smaller than JPG at the same quality.
• ✓Compress all images before uploading to WordPress, Shopify, or any CMS.
• ✓Aim for images under 200KB for above-the-fold content, under 500KB for everything else.

Resizing vs compressing: which do you need?

Resizing reduces the pixel dimensions of an image (e.g. from 4000×3000px to 1200×900px). This is the biggest factor in file size — a 4K image has 11× more pixels than an HD image.

Compressing reduces the file size without changing the pixel dimensions, by adjusting quality and encoding.

For the best results, resize first (to the target display size), then compress. Use PDFSpot's Image Resizer to resize, then the Image Compressor to optimise.