Compress PDF
Shrink PDFs in your browser — nothing is uploaded.
How to compress a PDF offline, without uploading
- Drop a PDF above — it is analyzed locally in your browser.
- Pick a preset. Blackbar tries several strategies (lossless repacking, re-compressing embedded images, and full rasterization for scans) and keeps whichever is smallest.
- Download the result with a before/after size comparison. If nothing beats your original, we say so instead of handing you a bigger file.
FAQ
Why did it say my PDF is already compact?
Text-based PDFs are often tiny already; re-encoding them as images would only inflate them. Blackbar refuses to produce a file larger than your original — many tools don’t.
Will my text stay selectable after compression?
With the repack and image-recompression strategies, yes. Only the rasterization strategy (used for scanned documents) turns pages into images.
What compresses best?
Scans and image-heavy documents — often 40–80% smaller. Pure-text contracts and invoices have little to squeeze.
Is my file uploaded?
No. Compression runs fully in your browser on this static site; it works offline too.
怎么离线压缩 PDF（不上传）
- 把 PDF 拖进上面的框——文件在浏览器里本地分析。
- 选择档位。Blackbar 会同时尝试多种策略（无损重打包、重压缩内嵌图片、对扫描件整页栅格化），自动保留最小的结果。
- 下载结果并查看前后体积对比。如果压不过原文件，会直接告诉你，而不是塞给你一个更大的文件。
常见问题
为什么提示我的 PDF 已经很紧凑？
文字型 PDF 本身往往就很小，把它们转成图片只会变大。Blackbar 拒绝输出比原文件更大的结果——很多工具做不到这一点。
压缩后文字还能选中吗？
用重打包和图片重压缩策略时可以。只有对扫描件使用的栅格化策略会把页面变成图片。
什么样的文件压缩效果最好？
扫描件和图片多的文档——常见能缩小 40–80%。纯文字的合同、发票本身没什么水分。
文件会被上传吗？
不会。压缩完全在你的浏览器里进行，本站是静态页面，离线也能用。