How image compression works
Understand quality, dimensions and why a smaller image is not always possible.
Two ways to make a smaller file
Lossless encoding represents the same pixels more efficiently. Lossy encoding trades some detail for fewer bytes. JPEG and WebP quality settings control this trade-off. PNG re-encoding may be larger than an already optimized source.
Dimensions are a separate control
A 2000 × 2000 image contains four million pixels; a 1000 × 1000 image contains one million. Reducing dimensions can save substantial space, but removes detail. Regular compression preserves dimensions; target-size tools may reduce them after lowering quality.
Compare the real result
Inspect edges, text and gradients in the output. Nexurivo reports the actual Blob size in decimal kilobytes (1 KB = 1000 bytes). If regular compression creates a larger file, the original is offered instead. No savings are invented.