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Absolutoolには、データ形式、マークアップ言語、エンコーディング、単位、数値システムをカバーする22の変換ツールが含まれています。JSON、CSV、YAML、XML、TypeScript、Markdown、HTML間でファイルをアップロードせずに変換 · すべてブラウザ内で処理されます。

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Why So Many Converter Tools

Every developer, designer, writer, and analyst encounters file format mismatches multiple times a week. A spreadsheet from a colleague comes as CSV but your tool wants JSON. A marketing team sends a HEIC photo from their iPhone but the website only accepts JPG. A devops engineer needs to convert an Apache config to nginx, an OAuth secret to URL-safe Base64, or a server log timestamp to a readable date. The converter tools in this category handle the common cases without any of the friction of installing yet another command-line utility or signing up for yet another web service. Each is a single page; each works in seconds.

The tools fall into roughly six clusters: data formats (JSON, CSV, YAML, XML, TypeScript), markup languages (HTML and Markdown in both directions), encoding (Base64 in text and image forms, URL encoding, hex), image formats (HEIC→JPG, ICO, JPG↔PNG, SVG→PNG, generic image converter), number systems (binary↔text, decimal↔binary↔hex↔octal, Roman numerals, number-to-words), and spreadsheet viewers (CSV and Excel preview without opening Excel). Each tool is purpose-built for one direction so the interface stays small. If you need a feature in the reverse direction, look for the matching tool.

Lossless vs Lossy Conversion

Conversions between text formats (JSON↔CSV, HTML↔Markdown, base64 encode/decode) are lossless: the round-trip preserves all the original information, though formatting choices like indentation or column order may differ. Conversions between image formats are usually lossy: HEIC→JPG re-encodes the pixels through JPEG's DCT compression, losing detail; PNG→JPG drops alpha channel transparency and applies the same DCT pass; only PNG↔WebP can be done with PNG's lossless mode preserved. Knowing whether your conversion is lossy matters when the file might be re-converted later: three lossy generations of a photo can produce visible degradation. The image-converter tool on this site reports the quality setting it uses for each output format.

Vector to raster conversion (SVG→PNG) is fundamentally lossy in a different way: vectors describe shapes mathematically, rasters describe pixels at a fixed resolution. Once you've rendered a vector at 1024×1024, that PNG has no information about the original curves. The SVG-to-PNG tool here lets you specify the output resolution so you can render at the size you need. If you may need a larger size later, save the SVG itself, not the PNG. Number-system conversions (decimal↔binary↔hex) are lossless because the underlying value is the same integer in different notations. Conversions between Markdown and HTML are lossless for the subset of features both support; HTML-only features (script tags, custom elements) are dropped on the way back to Markdown.

When You'd Actually Use Each Converter

JSON conversions show up everywhere in API work: a vendor returns CSV from a report endpoint, your code wants JSON; a config file is in YAML, your validator needs JSON; a TypeScript codebase needs type definitions from a sample JSON response. Each direction has its tool here, and each runs on your data without uploading it (the Base64 of a 2MB image stays in your browser tab). HTML and Markdown conversions are the writer's daily bread: drafting in Markdown for speed, exporting to HTML for a CMS, or pasting rich-text from Word into Markdown to add to a documentation repo. The tool preserves links, lists, tables, and code blocks.

Base64 is the universal "binary-as-text" encoding, used for inline images in HTML, JWT payloads, OAuth tokens, certificate PEM blocks, and email attachments (MIME). The Base64 tools here support both string and file inputs; the image variant produces a data URI you can paste straight into a <img src=...> tag. Number-base conversion is what you do when reading hex color codes, decoding 0x-prefixed memory addresses while debugging, or learning binary. Roman numerals come up in copyright dates, monarch numbering, and movie sequels; the calculator handles values up to 3999 (the traditional Roman maximum) plus the extended overline notation for larger numbers used in academic contexts.

Conversion Limits in the Browser

Browser-based converters are bound by the tab's memory budget, typically 4GB on a modern desktop and 1-2GB on a mobile device. For text formats this rarely matters: a 100MB JSON file is large but well within the budget. For image conversions the math is different: a 50-megapixel photo decoded into RGBA takes 200MB of memory before the converter even starts work. The image-converter tool watches for these limits and downscales or warns before attempting an out-of-memory operation. If you're doing batch processing of hundreds of large images, a desktop tool like ImageMagick or a build pipeline using Sharp will be faster and won't risk a browser tab crash.

The HEIC→JPG converter is a special case because HEIC decoding is not built into most browsers (Safari supports it; Chrome and Firefox don't natively). The tool ships a WebAssembly HEIC decoder that adds a one-time download of about 500KB but then converts at near-native speed. Once cached, the decoder is reused for every HEIC file you convert in the same session. The same pattern applies to RAW (DNG, NEF, ARW) formats: those require dedicated decoders far larger than 500KB and aren't included here. For RAW conversion, dedicated software like Lightroom or RawTherapee is appropriate.

Frequently Asked Questions