How much can the tool reduce my PDF size?

Results vary. PDFs that contain many redundant objects, uncompressed streams, or high-resolution embedded images see the largest reductions (30–70%). PDFs already optimised by tools like Acrobat may see little or no reduction.

Does compression affect quality?

The tool uses mupdf's lossless compression passes (object removal and stream compression) by default. It does not downsample images, so visual quality is preserved.

Why did my file get larger after compression?

This can happen if the PDF was already maximally compressed and adding mupdf's compression headers adds a small overhead. The tool will still let you download the result.

Is there a file size limit?

The tool accepts PDFs up to 25 MB. Very large PDFs may take longer to process as the mupdf WASM module works through the document in your browser.

PDFを無料でオンライン圧縮 — ファイルサイズを縮小

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品質を保ちながらPDFのファイルサイズを縮小 — 画像を再サンプリングしてストリームを最適化し、即座にダウンロード。

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使い方

3ステップでPDFを圧縮する

1
Upload your PDF
Drag and drop your PDF onto the tool or click to browse. The file loads directly in your browser — never sent to any server.
2
Compression runs automatically
mupdf (a professional PDF processing library compiled to WebAssembly) analyses and compresses the document — removing unused objects and recompressing images and fonts.
3
Download the smaller PDF
The tool shows the original size, compressed size, and percentage saved. Click 'Download compressed PDF' to save the result.

Signvoyを選ぶ理由

本物の圧縮、本物のプライバシー

Powered by mupdf WASM

mupdf is the same engine used in professional PDF applications. It removes unused objects, recompresses fonts and images, achieving real file size reductions.

Instant results with size report

The tool shows you the original size, compressed size, and percentage saved before you download — so you know exactly what you're getting.

Your file never leaves your device

The entire compression runs locally in your browser using WebAssembly. Nothing is uploaded or stored anywhere.

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この無料ツールはセルフサービスの一段階ドキュメント作業をカバーします。Signvoyの完全プラットフォームは、ビジネスに必要なすべてを追加します：複数の署名者への送信、署名順序の強制、改ざん防止の監査証跡の取得、リマインダーの自動化、完成したすべてのドキュメントへの完了証明書の添付。

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REST API & Webhook
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よくある質問

How much can the tool reduce my PDF size?: Results vary. PDFs that contain many redundant objects, uncompressed streams, or high-resolution embedded images see the largest reductions (30–70%). PDFs already optimised by tools like Acrobat may see little or no reduction.
Does compression affect quality?: The tool uses mupdf's lossless compression passes (object removal and stream compression) by default. It does not downsample images, so visual quality is preserved.
Why did my file get larger after compression?: This can happen if the PDF was already maximally compressed and adding mupdf's compression headers adds a small overhead. The tool will still let you download the result.
Is there a file size limit?: The tool accepts PDFs up to 25 MB. Very large PDFs may take longer to process as the mupdf WASM module works through the document in your browser.

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