Free Online Image Converter
Convert images between JPG, PNG, WebP, HEIC, GIF, BMP, TIFF, SVG and more. Free, fast, and secure — no signup, no watermark.
| ファイル名 | サイズ | 変換先 |
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ファイルと選択した出力形式を確認しています。
About Free Online Image Converter
Image conversion is the process of translating a picture from one file format to another — say, from a JPEG snapshot into a lossless PNG, or from an iPhone HEIC into a universally-supported JPG. It sounds simple, and for a lot of tools it just is: pick a file, pick a target, download the result. What most tools don't tell you is that every conversion involves trade-offs, and those trade-offs directly affect image quality, file size, transparency, and how the image behaves on the web, in print, or inside a design tool.
Getting a conversion right means understanding what the source format actually stores, what the target format can preserve, and what gets thrown away in between. This overview covers the underlying mechanics so you can make deliberate choices rather than hoping the default settings work out.
Lossy vs. lossless — the choice that matters most
Every image format falls into one of two camps. Lossy formats (JPG, WebP, HEIC, AVIF) discard visual information you're unlikely to notice, then compress what's left aggressively. That's why a 12-megapixel photo can land in a 2 MB JPG instead of a 20 MB raw. Lossless formats (PNG, TIFF, BMP, WebP-lossless) preserve every pixel exactly as-is, at the cost of much larger files.
As a rule: photographs go to lossy because JPEG-family compression is calibrated to human perception. Screenshots, illustrations, diagrams, logos, and anything with sharp edges or flat colour blocks go to lossless because lossy compression introduces visible ringing and haze around those edges.
The common formats at a glance
| フォーマット | 圧縮 | Alpha | こんな方に最適 |
|---|---|---|---|
| JPG | ロッシー | いいえ | Photos, web images |
| PNG | ロスレス | Yes (8-bit) | Screenshots, logos, UI |
| WebP | Both | はい | Modern web delivery |
| AVIF | Both | Yes (10-bit) | Next-gen web (2025+ browsers) |
| HEIC | ロッシー | いいえ | iPhone/iPad native |
| TIFF | Both | Yes (16-bit) | Print, archival, scanning |
| GIF | ロスレス (インデックス付き) | はい (1 ビット) | Short animations only |
| SVG | 該当なし (ベクター) | はい | Icons, logos, illustrations |
Colour, transparency, and metadata — what survives the trip
Two files can have the same visible pixels and still differ in ways that matter. A conversion tool preserves — or drops — these three things:
- Colour profile. sRGB is the universal web default. Adobe RGB and ProPhoto have wider gamuts, but if the profile is stripped during conversion, colours may shift on-screen.
- Alpha channel. PNG、WebP、および TIFF には透明性があります。 JPG と HEIC はそうではありません。透明な PNG を JPG に変換すると、透明度が白い (または設定可能な) 背景に平坦化されます。
- EXIF metadata. カメラ モデル、GPS 座標、キャプチャ時間は JPG および HEIC ファイル内に保存されます。 EXIF を削除せずに JPG をソーシャル メディアにアップロードすると、位置データが公開されてしまいます。ほとんどの iFormat 変換では、デフォルトで EXIF が保持されます。プライバシーが重要な場合は、明示的に削除できます。
Choosing a target format — a short decision tree
- Delivering to a website in 2026? に変換 WebP if you support browsers back to 2020, or AVIF if you're modern-only. Both cut file size roughly 30% versus JPG at equivalent quality.
- Sending to a print shop? に変換 TIFF (or high-quality JPG if the print house asks). Preserve the source colour profile.
- Sharing an iPhone photo with a Windows or Android user? Convert HEIC to JPG. HEIC support on non-Apple systems is spotty.
- Uploading a logo or icon to a design tool? Use PNG for raster or SVG for vector. Never JPG — the compression artifacts show around sharp edges.
- Compressing for email? JPG at 75% quality is nearly always the smallest usable option.
Where lossy compression hides its damage
Every time a lossy format is decoded and re-encoded, quality drops. This "generation loss" stacks: converting a JPG to WebP and back three times will visibly degrade the image, even though each individual step looks fine. If you'll process an image multiple times — editing, resizing, converting — keep a lossless copy of the original and use it as the source each time.
The other trap is over-compression. JPG at 40% quality shows blocky artifacts in flat areas and ringing around edges. Most humans can't tell 80% quality from 100%, but 60% is usually where the degradation becomes obvious on a good display.
What every iFormat image converter does the same way
All the tools listed below share the same processing pipeline: uploads are TLS-encrypted, files are processed on isolated per-request workers, results are available immediately, and both the upload and output are permanently deleted within 30 minutes. No ads, no third-party trackers, no watermarks on paid tiers. Where the conversion can run entirely in your browser (basic format swaps, thumbnails, colour-space changes), we do that — the file never leaves your device.
How to convert an image, step by step
Every iFormat image tool follows the same flow. If you've used one, you already know how the others work.
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Choose the right tool for your source and target format
Start with what you have and where you're going. JPG to PNG, HEIC to JPG, PNG to WebP — each is a dedicated tool with settings tuned for that specific pair. If you're not sure which target to pick, the tool's page includes a short "when to use" note.
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Drop or select your files
Drag one or more images into the drop zone, or click to browse. On the free tier a single file up to 10 MB is supported; Pro handles batches of up to 20 files at once, each up to 1 GB. Batch conversions preserve original filenames with the new extension appended.
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Adjust quality, if the format supports it
For lossy targets (JPG, WebP, HEIC), pick a quality level between 60 and 95. 85 is a safe default that matches what most cameras and design tools use. Higher means larger files with diminishing visual return; lower means smaller files with visible artifacts. Lossless targets have no quality slider — every pixel is preserved.
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変換してダウンロード
The output is ready in the browser. Download individually or as a ZIP for batch jobs. Both the upload and the converted files are permanently deleted from our servers within 30 minutes — usually much sooner. Nothing is retained.
Tips people usually learn the hard way
- Never convert JPG → PNG expecting quality to improve. PNG is lossless, but it can't undo JPG artifacts. The result is a bigger file that preserves the same flaws.
- Watch alpha when the target doesn't support it. Converting a transparent PNG to JPG will flatten the transparency onto a background colour. Check the result before shipping it.
- Strip EXIF for public uploads. Camera photos carry GPS coordinates, capture time, and device model in EXIF metadata. Social platforms strip most of it, but not all — if location matters, remove metadata explicitly.
- Batch resize before batch converting. A 24-megapixel source doesn't need to become a 24-megapixel WebP for a website. Resize first, then convert.
When you actually need to convert an image
Real scenarios, real reasoning — not "so you can use it on the web."
Sharing iPhone photos with people who don't own iPhones
Since iOS 11, iPhones save photos as HEIC to save storage. HEIC is efficient but unsupported on most Windows apps, older Android versions, and many CMSes. Converting HEIC to JPG makes the photo openable everywhere at the cost of a slightly larger file. This is the single most common conversion request we see.
Cutting website page-weight to improve Core Web Vitals
Converting a JPG hero image to WebP typically drops file size by 25-35% at the same visible quality. AVIF cuts another 20% but still lacks universal browser support. If your Largest Contentful Paint (LCP) is dragging, converting your top three above-the-fold images is often the fastest win.
Adding transparency to a photo (or removing it)
JPG has no alpha channel — if your source is JPG and you need transparency (say, for a product mockup), converting to PNG or WebP is a prerequisite. Going the other way (PNG → JPG) forces you to flatten transparency onto a background, so it's worth previewing the result before you commit.
Meeting an application's format rules
Passport photo portals expect JPG. Adobe Illustrator prefers PNG or SVG for imports. Government forms often require sub-200 KB JPG. WordPress rejects HEIC uploads unless you install a plugin. A quick conversion sidesteps the rejection and gets you back to whatever you were actually trying to do.
Turning scans and screenshots into archival files
For scanned documents that need to stay legible for years, TIFF is the format of record. It's lossless, supports multi-page, and preserves colour profiles. Converting scans to TIFF once means every future edit or export uses the same clean source.
Preparing assets for print
Print shops want high-quality JPG (95-100%), TIFF, or PDF — never WebP, HEIC, or AVIF. Colour profile matters too: sRGB for anything screen-adjacent, CMYK for offset print. If your source is a screenshot in PNG, converting to high-quality JPG or TIFF is usually the right prep step.
Not sure which conversion you need? Skim the tool grid below — each entry is labelled with the source and target format, and the tool page itself will tell you what the conversion preserves and what it drops.