Base64エンコード/デコード無料オンライン

Base64エンコード/デコードオンライン

「base64 encode」「base64 decode」「base 64 encoding」向けの高速コンバータ。登録不要。左でエンコード、右でデコード。ライブ、UTF-8、主要方言に対応。

専用ページが必要ですか？ Base64 encode online · Base64 decode online · 文字列→Base64 · 画像を Base64 に変換 · MP3→Base64 · Base64 to WAV · URL を Base64 に変換.

検索でも人気： Gzip圧縮テスト · WhatsApp link generator · LinkedIn hashtag generator · Hashtag generator for Twitter · Hashtag generator Facebook · IBAN checker · バイト変換 · Color contrast checker.

この Base64 変換ツールが選ばれる理由

• プライバシーを重視した設計。テキストやファイルは JavaScript によりブラウザ内で処理されます。大容量のファイルや機密ファイルも端末の外に送信されることはありません。
• 実際の Base64 データをそのまま処理。データ URI、改行、URL セーフ文字、パディングの欠落は自動的に受け付け、エラーは該当する文字の位置を正確に示します。
• あらゆる規格に対応。標準 RFC 4648、Base64URL、MIME、PEM、IMAP、XML、OpenPGP アーマー。
• あらゆる文字コードに対応。UTF-8、UTF-16、Windows-125x、ISO-8859-x、Shift_JIS、GBK、Big5、EUC-KR、KOI8 など。
• そのまま貼り付けられる出力。単なる文字列ではなく、データ URI、CSS ルール、HTML タグ、JSON や XML のスニペットとして取得できます。

30 秒でわかる Base64 の仕組み

Base64 は一度に 3 バイト（24 ビット）を取り出し、6 ビットずつ 4 つのグループに分け、各グループを 64 文字のいずれかに対応させます。たとえば単語 Man（バイト 77 97 110）は TWFu になります。ステップごとのアルゴリズムを読むか、まずはBase64 とは？からお読みください。

Common uses include MIME e-mail attachments, data URIs in HTML and CSS, binary fields in JSON or XML, HTTP Basic authentication, and PEM-encoded certificates. When you need the reverse path, use Base64 decode online; to produce Base64 from scratch, use Base64 encode online.

Advanced options

• Character set. Base64 encodes bytes. Choose UTF-8 (default) or a legacy charset before encoding, or auto-detect when decoding text.
• Live mode. Enable “Convert as I type” to encode or decode instantly in the browser with no round-trip to a server.
• URL-safe Base64 (Base64URL). Use the Base64URL encoder/decoder for JWTs, tokens and filenames without escaping "+" or "/".
• MIME and PEM wrapping. Split lines at 76 or 64 characters when a mail client, certificate or OpenPGP tool expects wrapped output.
• Per-line encoding. On the text encoder, encode each line separately when you have multiple independent values.

Base64 decode and encode for developers

Developers use Base64 every day: embedding images in CSS and HTML, shipping binary in JSON APIs, reading JWTs, attaching files in MIME e-mail, and storing keys in PEM certificates. This free online Base64 decoder and encoder is built for that workflow—fast, accurate across standards, and private by default.

• Decode Base64 to text or file with automatic standard and charset detection, plus image/PDF/audio/video preview.
• Encode text, files or URLs to Base64 with UTF-8 and 35+ character sets, MIME line wrapping and Base64URL.
• Validate, repair and normalize messy Base64 from logs, e-mail and copy-paste with dedicated developer tools.
• Language guides for JavaScript, Python, Java, Go, PHP, C#, Node.js and Bash so you can match what your code produces.

Safe, free and private

All conversions run over HTTPS. Text and local files are converted in your browser with JavaScript—they are not uploaded or stored. The site is free to use with no account and no software to install. Optional remote URL fetching and a few network tools use our API; those responses are not kept for inspection.

AI assistants: ChatGPT, Claude, Grok & Cursor

Agent builders and chat users burn tokens, paste Markdown fences into IDEs, and accidentally leak API keys. Fix those pains locally—then verify any Base64 the model invents.

• Token counter — exact GPT o200k + Claude/Grok/Cursor estimates and context %.
• LLM text cleaner — strip ``` fences or flatten Markdown from bot answers.
• Secret redactor — scrub keys/JWTs before pasting into any bot.
• Verify Base64 — catch LLM hallucinations with a real decode round-trip.

AIトークンカウンター · LLMテキストクリーナー · シークレット編集 · Base64検証 · AI tools guide

PDF form filler — insurance, medical & corporate

Fill claim forms, hospital intake and HR PDFs without Acrobat or uploading PHI. Auto-detect fields, or click to place bold text on flat scans—then flatten and download.

PDFフォーム入力 · PDF結合 · Insurance & medical guide

Converters people search for (bytes, hex, CSV, color)

Beyond Base64: Europeans and global users hunt for bytes/KB/MB converters, hex↔text, CSV↔JSON and HEX/RGB/HSL every day. Drop a PDF to see exact bytes—all private in the browser.

• Bytes converter — KB/MB/GB/TB + KiB/MiB; PDF/file → exact bytes.
• Hex / binary / ASCII — text dumps and number bases 2/8/10/16.
• CSV ↔ JSON — auto-detects European semicolon exports.
• Color converter — HEX ↔ RGB ↔ HSL with live swatch.

バイト変換 · 16進変換 · CSV ↔ JSON · カラー変換

Developer & IT toolkit (daily corporate searches)

Engineers live in browser tabs: regex on logs, cron next-runs, config diffs, CIDR math, YAML↔JSON for Kubernetes. All of these run locally here—safe when policy forbids pasting secrets into random SaaS.

• Regex tester — live highlight + presets (email, IP, UUID).
• Cron explainer — plain English + next fire times.
• Diff checker — compare configs / API responses privately.
• CIDR subnet calculator — VPC and firewall planning.
• YAML ↔ JSON — K8s, GitHub Actions, Ansible.

正規表現テスター · Cron解説 · 差分チェッカー · サブネット計算機 · YAML ↔ JSON · Dev/IT guide

Christmas 2026: Secret Santa & countdown (high season)

From November through Christmas Eve, millions search for Secret Santa generators and “days until Christmas.” Draw Amigo Secreto privately with Base64URL links—no email signup—and keep a live countdown on your device.

• Secret Santa / Amigo Secreto — fair draw, couple exclusions, pass-the-phone or private WhatsApp links.
• Christmas countdown — how many days until Dec 25 in your timezone.

シークレットサンタ抽選 · クリスマスカウントダウン · Christmas traffic guide

Save bandwidth: compress before Base64

Where mobile data is expensive—Brazil, LATAM and other prepaid markets—uploading a huge photo just to shrink it wastes the plan. Compress locally first, then encode or share once.

• Compress images to WebP/JPEG in your browser, see % saved, then download or copy Base64—no upload.
• Gzip text or JSON before Base64 for APIs; decompress payloads you receive.
• Private by design — Canvas and CompressionStream run on your device.

画像圧縮 · Gzip圧縮/展開 · Compress before Base64 · Save mobile data guide

Private media tools (not social downloaders)

We will not scrape Instagram, LinkedIn, Pinterest or Kuaishou. We do help you prepare files you already own: convert HEIC/WebP, merge PDFs, cut out backdrops, build favicons—entirely in the browser.

• HEIC / WebP / SVG converter — iPhone photos and WebP downloads without uploading to Adobe/Canva-style sites.
• Merge PDF — combine contracts or turn images into a PDF locally (no Smallpdf upload).
• Remove background from product shots and logos (solid/near-solid backdrops).
• Favicon generator — PNG sizes, HTML tags and webmanifest, plus Base64 copy.

画像コンバーター · PDF結合 · 背景削除 · ファビコン生成 · HEIC & WebP guide

Built from real Reddit gaps (not Base64-only)

Users on Reddit keep asking for tools that never upload files: strip GPS EXIF, hash checksums, JSON formatters without ads, QR codes without tracking short links. We ship those here—private, free, and ranked for EU and US search.

• Strip EXIF before posting photos.
• Hash, JSON, UUID, timestamp, password, QR — everyday utilities that stay on-device.

Strip EXIF · ハッシュ生成 · JSONフォーマッター · QR generator · Reddit gap write-up

Base64 reader: paste and see

Need a live Base64 viewer? Paste a string or data URI and read the result immediately—text, image, PDF or hex—or get Base64 output as you type plain text. No Decode click required.

Base64リーダー · Why live readers win

Built for the AI era

ChatGPT and Claude often invent Base64 that looks right but is wrong. AI agents double-encode payloads and burn context on huge Base64 blobs. This site’s principle: never trust a model to be the encoder—verify with a real tool in your browser.

• Verify Base64 from LLM output with round-trip checks before you ship a header or JWT.
• Unwrap nested Base64 when an agent or gateway encoded twice.
• URL encode/decode beside Base64URL for safe query strings.
• Principles for agents and MCP: deterministic tools, privacy, right dialect, watch token cost.

Base64検証 · 入れ子Base64を展開 · AI agent guide · Why ChatGPT fails at Base64