画像圧縮ツール
画質を落とさずにJPG、PNG、WebP画像の容量を大幅削減。目標KB指定や比較プレビュー対応。サーバー送信ゼロでプライバシー完全保護。
or drag & drop here
Paste from clipboard with Cmd+V · Multiple files supported
Supported: JPG · PNG · WebP · AVIF · HEIC
- Never uploaded
- No watermark
- No sign-up
- No server upload limits
How It Works
Simple 3-step compression powered entirely by your local browser
画像をドロップ
JPG, PNG, WebP, AVIF, HEICに対応。サーバー送信なしで端末内で即時読み込み。
モード選択
バランス重視モードまたは目標KB/MB指定。保存前に画質の比較確認が可能。
即座に保存
個別保存または全ファイルを一括ZIPでダウンロード。
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
Specialized Tools & Guides
Purpose-built browser tools solving specific format and platform constraints.
WebP Compressor
Compress static WebP images free in your browser. Adjust quality or target size, compare the result, and download without uploading your images.
PNG Compressor
Compress static PNG images locally in your browser. Keep PNG output for transparency, compare dimensions and file size, and download the result.
HEIC to JPG Converter
Convert iPhone HEIC photos to standard JPG format locally in your browser. Fast, free batch conversion with zero privacy leaks.
画像フォーマット別ローカル圧縮と実測比較
JPG, PNG, WebP, AVIFをブラウザ内でWebAssembly処理。バランスモードと目標サイズモードの実測削減データです。
| フォーマット・用途 | 元サイズ | バランスモード | 目標サイズ指定 | 平均削減率 | 推奨用途 |
|---|---|---|---|---|---|
| JPG 写真 | 4000×3000 (5.8 MB) | 840 KB (Q82) | 500KB以下に固定 | ~85% | Web掲載・SNS共有 |
| PNG スクショ / ロゴ | 2560×1440 (3.2 MB) | 520 KB | 300KB以下に固定 | ~83% | 透過維持・文字のシャープさ保持 |
| WebP 画像 | 1920×1080 (1.4 MB) | 280 KB | 200KB以下に固定 | ~80% | 高速ページ表示（PageSpeed向上） |
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