Glossary
What is compression ratio?
MarkdownWhat it is
You divide the original size by the new size. Higher means more shrinking. Lossy formats reach higher ratios than lossless ones.
Why it matters on a Mac
Files that are already compressed, such as MP4 videos, JPEGs and many PDFs, have little room left, so the ratio can be small.
How to check it on macOS
Select the original and the compressed copy in Finder and press Command-I on each. Compare the sizes.
How Toolbox handles it
Compress Video, Compress Images and Compress PDF write smaller copies to a new folder and keep your originals. If a PDF cannot be made smaller, Toolbox keeps the original as it is.
Frequently asked questions
What is a good compression ratio?
It depends on the content. Photos and video can shrink a lot, plain text PDFs very little.
Does higher compression mean lower quality?
For lossy formats, usually yes.
Why did my PDF not get smaller?
It was mostly text or already compressed.
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