1. Getting Started

From the homepage, click any tool card to open it. Each tool loads instantly with the content you last used (your editor content is auto-saved to your browser's encrypted local storage).

Use the sun/moon button in the top-right corner to toggle between Light and Dark mode. Your preference is saved automatically.

Use the EN / ID toggle in the header to change the interface language. Your choice is remembered and applied before the page paints, so the copy never flashes in the other language.

2. Development Tools

REST API Client /restapi/

A full-featured HTTP client that runs in your browser.

• Request Builder — choose method (GET, POST, PUT, DELETE…), set URL, add headers and body
• Environments — define variables (e.g. {{BASE_URL}}, {{TOKEN}}) and switch between environments (dev, staging, prod)
• Auth — supports Bearer token, Basic auth, and API key injection
• Collections — save and organize frequently used requests
• History — automatically logs your last requests for quick replay
• Test Scripts — write post-response assertions in JavaScript

JSON Viewer /json/

• Paste or type JSON — the tree view updates in real-time
• Switch between Tree, YAML, and CSV views via the tabs above
• Use Search (Ctrl+F) to filter nodes in tree view
• Click any node path to copy it to clipboard
• Use Fetch URL to load JSON directly from a URL
• Sort keys A→Z with the Sort button

Viewer Tools /javascript/ /html/ /css/ /xml/ /text/

All code viewer tools share a consistent interface:

• Beautify — format code with proper indentation (Ctrl+Shift+F)
• Minify — compact the code to reduce size
• Find — open the in-editor search bar
• Import — load a file from your device
• Export — save the current content as a file
• Copy — copy all content to clipboard
• Clear — reset the editor (with confirmation)

The HTML Viewer additionally provides a live preview panel and viewport size presets (Desktop / Tablet / Mobile).

The Text Toolkit includes transform operations (upper/lower/title case, trim, sort lines, deduplicate) and a side-by-side diff comparison mode.

Markdown ↔ HTML /markdown-html/

Convert in both directions, with a live preview beside the editor.

• Preview — GitHub-flavoured Markdown rendered as you type
• HTML — switch tabs to read, copy, or save the generated markup
• From HTML — paste markup into the editor to convert it back to Markdown
• Export document — download a standalone HTML file with typography, container width, font, and an optional table of contents and theme toggle

3. Security & Identity Tools

Hash Generator /hash/

Type or paste text — all hash values update in real time as you type.

• Algorithms: MD5, SHA-1, SHA-224, SHA-256, SHA-384, SHA-512
• Use the Verify tab to check if a string matches a known hash
• Click the copy icon next to any hash row to copy that specific value

Transcode /transcode/

Encode and decode between formats. Toggle the mode switch to flip between encode and decode.

• Base64 — standard Base64 encoding/decoding
• URL Encode — percent-encoding for query strings
• Hex — UTF-8 text to/from hexadecimal
• HTML Entities — escape/unescape HTML special characters
• JWT Decode — inspect JWT header and payload without verification

Encryptor /encryptor/

• Enter your text and a passphrase, then click Encrypt
• The output is a Base64-encoded AES-256-GCM ciphertext
• To decrypt, paste the ciphertext and the same passphrase, then click Decrypt
• Use Swap to move output back to input for chained operations
• Keyboard: Ctrl+Enter to encrypt, Ctrl+Shift+Enter to decrypt

Signer & Verifier /signer/

• Enter a message and a secret key, click Sign to generate an HMAC-SHA256 signature
• To verify, paste the message, key, and signature — click Verify
• Keyboard: Ctrl+Enter to sign, Ctrl+Shift+Enter to verify

SSL Toolkit /ssl/

Three tools in one, accessible via the pill tabs:

• Decode Certificate — paste a PEM certificate to inspect subject, issuer, validity dates, serial, SANs, and signature algorithm
• Generate CSR — fill in the form to generate a Certificate Signing Request and private key (RSA 2048-bit, browser-side)
• Key Matcher — paste a certificate and private key to verify they are a matching pair

4. Keyboard Shortcuts

5. Privacy & Data

See the full Privacy Policy for details on how browser storage works and what (very little) data is stored.

6. Tips & Tricks

• Auto-save — editor content is saved automatically as you type. Refreshing the page restores your last session.
• Import & Export — use the Import button to load any text file, and Export to save your work as a file.
• Offline use — once loaded, tools work without an internet connection (except REST API Client, JSON Fetch, and Google Fonts).
• Theme — toggle Light/Dark with the sun/moon icon. Your choice persists across all tools.
• Multiple tabs — each tool is a separate URL — open several in different tabs simultaneously.
• REST API environments — wrap variable names in double curly braces: {{VARIABLE}} — they are replaced at request time from the selected environment.

7. Browser Support

One Code requires a modern browser with support for:

• ES2020 JavaScript (dynamic import, optional chaining, nullish coalescing)
• WebCrypto API (AES-GCM, HKDF, SubtleCrypto digest)
• CSS Custom Properties (variables)
• localStorage

Recommended: Chrome 90+, Firefox 90+, Safari 15+, Edge 90+.

Internet Explorer is not supported.

8. Getting Help

One Code is built and maintained by PT Lancar Inovasi Digital. If a tool misbehaves or you want to suggest one, email contact@lancar.id. For security issues, follow /.well-known/security.txt instead of the general address.