PDF圧縮ツール

文字のベクター品質を損なうことなく、PDF内の画像や構造を最適化。履歴書や公的申請の2MB制限クリアに最適。サーバー送信なしで安全。

100% Local · Files Never Leave Your Device

Compression Mode

or drag & drop here

Paste from clipboard with Cmd+V · Multiple files supported

Supported: PDF

No server upload limit0 KB uploadNo watermark100% Free

Processing happens locally in your browser — nothing is uploaded.

Try a sample:

Never uploaded
No watermark
No sign-up
No server upload limits

How It Works

Simple 3-step compression powered entirely by your local browser

§ 01

Step 01

PDFを追加

PDFを選択またはドラッグ＆ドロップ。アップロード不要でローカル即時展開。

§ 02

Step 02

構造と埋め込み画像を最適化

ベクター文字を保持したまま、重い埋め込み画像のみをスマートに再圧縮します。

§ 03

Step 03

軽量化されたPDFを保存

処理完了後にダウンロード。文字はベクターのまま鮮明さを維持します。

Why Choose LessMB

The private, modern alternative to legacy cloud compressor websites

100% In-Browser Privacy

Zero bytes uploaded. Your personal photos, sensitive documents, and private videos never touch external servers or cloud storage.

Zero Queue & Instant Start

No waiting in cloud conversion queues or watching slow upload bars. Processing starts the millisecond you drop your file.

Hardware Acceleration

Harnesses WebAssembly SIMD and WebCodecs GPU encoding for high-fidelity compression directly on modern consumer hardware.

No Credit Consumption

Free tier compression uses your own device compute, meaning zero server credit drain for everyday single and batch tasks.

LessMB vs Traditional Cloud Compressors

See how client-side processing outperforms legacy server-based tools

Feature

Cloud Compressors

LessMB

Data Privacy

Files uploaded to 3rd-party servers

100% In-Browser (0 bytes uploaded)

Upload Latency

Minutes spent uploading large files

Instant (0s upload time)

Queue Wait Time

Enqueued during peak hours

Immediate local execution

Credit Limits

Depletes daily or monthly credits

No credit deductions for local compute

Target Size Accuracy

Rough percentage estimates

Dual-pass KB / MB target limits

Folder Tree Packaging

Rarely supported

Full folder hierarchy preserved in ZIP

Category Leaf Tools

Specialized Tools & Guides

Purpose-built browser tools solving specific format and platform constraints.

How to Compress a PDF on Mac

Learn how to compress a PDF on Mac with Preview or a local browser tool. Follow export steps, compare methods, and check text and images before sharing.

Launch Tool

3大典型PDF文書のローカル実測圧縮と鮮明度比較

PDFの肥大化原因は様々です。LessMBは「ベクター文字を絶対に画像化しない」方針を徹底し、印鑑や文字のシャープさを維持します。

文書種別	肥大化要因	元サイズ	圧縮後	削減率	鮮明度・品質	想定提出先
契約書・スキャン書類	300 DPI 非圧縮スキャン画像	16.4 MB	1.8 MB	~89%	150 DPIへダウンサンプル、押印や署名も明瞭	e-Gov / 行政・転職ポータル (2MB制限)
学術論文・研究レポート	重複フォントデータ・高解像度グラフ	8.2 MB	2.4 MB	~71%	数式や本文は完全ベクター、拡大しても鮮明	arXiv / 学会投稿 / メール送信
提案書・プレゼン企画資料	未圧縮の高解像度フルカラー写真	34.5 MB	6.8 MB	~80%	画像のみ再圧縮、レイアウトの崩れなし	社外メール添付 / チャット共有

Frequently Asked Questions

Everything you need to know about LessMB in-browser compression

Looking for other file formats? Back to LessMB Free Online File Compressor