About SDK.is
Free, fast, privacy-focused developer utilities — running entirely in your browser.
Our Story
We started SDK.is in 2024 because every developer in our team was using a different "JSON formatter" website at work — and most of them had become unusable. Pop-ups, full-screen ads, login walls, "upgrade to format JSON over 1 MB," cookie banners with seven layers of dark patterns. The actual tool — a textarea, a button, an output — was buried under fifty kilobytes of marketing.
We wanted somewhere to send a coworker a one-line link, have them paste a token or a JSON blob, and get the answer in under a second. So we built it. The first version was a single tool (JSON formatter) with one button. We kept adding tools as the team hit them in real work — JWT decoder when we needed to debug a SAML flow, hash generator when a backend service swapped algorithms, regex tester when we needed to write a path-rewrite rule.
Today the catalogue is over 23 tools deep, every one of them runs entirely in your browser, and the entire site loads in under one second on a 4G connection. The two-man rule we follow: a tool ships only if (a) at least two of us would have used it last week, and (b) it works without sending a single byte of your input to any server.
We monetise with display ads. We deliberately keep the ad density well below the industry average — usually one ad slot per page, none of them between you and the tool. The ad pays for the hosting; if the ad ever made the tool worse to use, we would move or remove it.
Our Mission
SDK.is exists to give working people a fast, friction-free toolbox for the developer utilities they actually need every day. We believe everyday utilities should be free, accurate, fast, mobile-friendly, and respect your privacy by default. Whether you are at your desk, on a train, or in a parking lot trying to settle a dinner bill, we want you to find your answer in seconds.
We measure success in three numbers: time-to-answer (target: under 3 seconds from cold load to result), inputs-to-answer (target: as few as possible), and bytes-of-your-data-on-our-servers (target: zero). Everything else is downstream of those numbers.
Long-term, our mission is broader than the current tool catalogue. We want SDK.is to be the place a friend recommends when you say "is there a calculator for that?" — and have you not feel a flicker of regret when you click the link.
Who We Are
SDK.is is operated by SDK Co., Ltd., a Korean software company founded in 2024 that builds developer-focused tools and free online utilities. Our team has shipped consumer and developer web products used by millions, and we apply that same attention to UX, accuracy, and speed to every developer utility on this site.
Beyond SDK.is, the same team operates JavaScript.ac (interactive JavaScript learning), SDK.is (developer utilities), SDK.bz (financial and crypto calculators), and SD.gy (everyday calculators). Lessons learned on one site — accessibility patterns, performance budgets, ad-density thresholds — get applied across all of them.
- Company
- SDK Co., Ltd.
- Founded
- 2024
- Focus
- Developer tools, calculators, free utilities
- Business Registration
- 871-81-03242
- E-Commerce Registration
- 2024-고양일산서-1820
- Address
- 4F, 127 Namseong-ro, Jeju-si, Jeju Special Self-Governing Province, Republic of Korea
What You'll Find on SDK.is
SDK.is ships 23+ developer utilities today, all free, all running 100% in your browser.
JSON Formatter & Validator
Format, minify, and validate JSON with inline error highlighting and tree view. Supports very large JSON files because parsing happens in your browser, not on a remote server.
Base64 Encoder / Decoder
Encode any string or binary file to Base64, including URL-safe variant. Handles UTF-8 cleanly and gives you copy-friendly output.
UUID Generator
Generate UUID v1, v4, and v7 in bulk. Each batch is created locally — useful for seeding test data or creating unique identifiers in scripts.
JWT Decoder
Decode and inspect the header and payload of any JSON Web Token. The token never leaves your browser, which matters when you are debugging production tokens.
Hash Generator
MD5, SHA-1, SHA-256, SHA-512, and HMAC variants. Drop in a string or a file and get the digest immediately.
Regex Tester
Test and debug regular expressions with live match highlighting, capture-group inspection, and a quick reference for tricky tokens.
Color Converter
Convert between HEX, RGB, HSL, and CMYK color spaces. Includes a colour picker and accessibility-contrast checker.
URL Encoder / Decoder
Percent-encode and decode URL components. Useful for query-string debugging and API testing.
Timestamp Converter
Convert between Unix timestamps (seconds and milliseconds) and human-readable dates across time zones.
JSON ↔ CSV / YAML
Convert tabular and structured data between common formats with a clear preview pane.
Markdown Preview
Live preview Markdown with GitHub-flavoured extensions, side-by-side editing.
QR Code Generator
Generate QR codes for URLs, text, Wi-Fi credentials, and contact cards. Download as PNG or SVG.
Our Principles
Free Forever
No paywalls, no premium tier. Ads keep tools free for everyone.
Privacy-First
All processing happens in your browser. Your data never leaves your device.
Fast by Default
Sub-second load times powered by Cloudflare's global edge network.
Open Access
No login, no signup, no email required. Just open and use.
Mobile-First
Every tool is touch-friendly and works great on phones and tablets.
No Dark Patterns
No fake countdown timers, no roach-motel cookie banners, no manufactured scarcity.
Technology Stack
We chose every piece of the stack to optimise for read speed, write speed, and long-term maintainability with a small team.
Our frontend is built on SvelteKit and TypeScript, styled with Tailwind CSS, and deployed to Cloudflare Pages. We use no traditional backend: pages are statically pre-rendered or generated at request time at the edge, calculator/tool logic runs entirely in the user's browser, and dynamic features that need persistence use the user's own localStorage.
This architecture has practical consequences for you. First, time-to-interactive is measured in tens of milliseconds, not seconds. Second, your inputs never leave your device, so there is no server log to leak. Third, our infrastructure cost is low enough that we can keep SDK.is free indefinitely without ever introducing a "Pro" tier.
Privacy Promise
All developer utilities on SDK.is run client-side in your browser. The text, files, or values you input are never transmitted to our servers. The only data we collect is standard, aggregated analytics (page views, country, device type) and AdSense-related cookies as described in our Privacy Policy. We never sell or share personal data, we never read your inputs, and we never use your activity to train machine-learning models.
If our ad provider changes its consent rules, we will update the consent banner immediately and post a clear changelog entry on the Privacy Policy page. We treat consent as a permanent design choice, not a compliance afterthought.
Contact Us
Have questions, suggestions, or feedback? We'd love to hear from you.
- General questions and feedback: contact@sdk.is
- Bug reports: please include reproduction steps, browser, and OS.
- Tool suggestions: tell us which calculation or utility you wish existed — real use-cases move our roadmap.
- Partnership and content collaboration: include "Partnership" in your subject line.
- Press and media: same e-mail address, with "Press" in the subject line.
Legal & Operator Information
SDK.is is operated by SDK Co., Ltd., a Korean corporation registered with the Republic of Korea's Ministry of the Interior and Safety and the Korean Fair Trade Commission.