What is image compression?
Definition
Image compression is the process of reducing the file size of an image. It works by storing the picture's data more efficiently (lossless) or by discarding detail the eye is unlikely to notice (lossy). The pixel dimensions can stay the same.
Why it matters for sellers
Product pages with many large photos load slowly, especially on mobile data. A shopper who waits on a gallery is more likely to leave, so lighter images help a listing do its job.
Marketplaces and shop platforms also set upload limits and may recompress files they receive. Compressing on your own terms lets you choose the balance between size and detail, instead of letting a platform decide for you.
How to do it with Instasize
The free Instasize Image Compressor works in your browser. You set a target file size or a quality level and compare the result with the original before saving.
- Upload your JPG, PNG or WebP images.
- Choose a target file size, or use the quality slider instead.
- Pick JPEG or WebP output, or keep the original format.
- Compare each result with the original, then download.
Related Instasize pages
Examples
Phone photo for a shop upload
A seller exports a full-resolution phone photo that is far too heavy for a product gallery. Compressing it to a lower file size keeps the product clear at normal viewing size.
Email attachment
A buyer asks for photos of an item, but the email client rejects the attachment as too large. Compressing the images lets them send.
Form with a size cap
A seller application asks for an ID photo under a stated size limit. Setting a target file size in the compressor works down to that cap.
Frequently asked questions
Does compressing an image reduce its quality?
It depends on the method. Lossless compression keeps every pixel exactly. Lossy compression removes some detail, which is often hard to see at normal size but can show up when the setting is too strong.
Is compressing the same as resizing?
No. Resizing changes the pixel dimensions. Compression changes how the data is stored, so the dimensions can stay the same while the file gets smaller.
Which format compresses best?
For photos, JPEG and WebP are lossy formats that make small files. PNG is lossless, so it stays larger. Pick JPEG or WebP when you need a smaller file.
Should I keep the original file?
Yes. Repeated lossy compression adds up, so always keep an untouched original and compress a copy.