ガイド
見た目を崩さずに画像を圧縮する方法
容量を減らしながら、Webで十分きれいに見える品質を保つ実践手順です。
圧縮はページ速度を上げるための作業です。リサイズ→品質比較→実ページ確認の順で進めると失敗を減らせます。
Resize before you compress
If the page shows an image at 1000px width, uploading a 3000px file wastes bandwidth.
Set dimensions close to real display size first, then compress for better results with fewer artifacts.
Choose format by image type
Use JPG for photos, PNG for graphics that need clean edges or transparency, and WebP when you want a strong size-to-quality balance.
Using the wrong format forces heavier compression and hurts quality faster.
Test a small quality range
Instead of guessing one value, compare nearby settings such as 80, 70, and 60.
Small drops often save a lot of size while staying visually acceptable.
- Check screenshot text readability.
- Look at faces and edges at normal zoom.
- Prefer slightly smaller files on mobile-first pages.
Review in real page context
Do not judge only from editor previews at extreme zoom.
Open your draft page on desktop and mobile to confirm the image still supports the content.
Keep one clean source file
Repeatedly compressing the same lossy file can stack artifacts.
Store one high-quality original and export fresh compressed versions for upload.
When this guide helps
- You need lighter images but still want a clean professional look.
- Your screenshots become blurry after compression.
- You want a repeatable quality check before upload.
- You need practical settings for mixed image types.
Aim for clear enough, not perfect
A practical quality target beats guesswork. Keep source files safe, export a web version, and publish the smallest version that still looks clear in context.