About SDK.ac
Free AI writing and prompt tools — no login, no upsell, and your text stays on your device.
Our Story
I started SDK.ac because I got tired of what "free AI tool" has come to mean on the web. Search for a free AI translator or a text summarizer and you land on the same three experiences: a login wall before you can type a single word, a tool that works once and then nags you to "upgrade for unlimited generations," or — worst of all — a site whose business model is quietly harvesting the text you paste in. I have pasted client emails, half-finished blog drafts, and snippets of proprietary code into sites like that before reading their privacy policies. Most people do. That is a problem.
What I actually wanted was embarrassingly simple: a page where you paste text in, press one button, and get a useful result out. No account, no credit counter, no "you have 2 free uses left today," no dark-pattern cookie banner between you and the textarea. So in 2024 I built the first version of SDK.ac — a single prompt generator with one input and one button — and kept adding tools whenever I hit a real need in my own work: a translator prompt tool when I was localising a product into four languages, a code explainer when I was onboarding a junior developer, an email writer when I realised I was rewriting the same three business emails every week.
Today SDK.ac hosts eight AI-focused tools, and every one of them follows the same rule the first one did: the tool must be usable within two seconds of the page loading, and your text must never be silently sent anywhere. Most of our tools are prompt builders — they take your input and your options and assemble a carefully structured, battle-tested prompt that you can paste into ChatGPT, Claude, Gemini, or whichever AI assistant you already use. The summarizer runs its extraction logic entirely in your browser. Nothing you type is transmitted to our servers, logged, or stored.
We keep the lights on with display advertising, and we are deliberate about it: the ad density stays well below the industry average, and no ad is ever placed between you and the tool you came to use. If an ad ever makes a tool worse, the ad moves or the ad goes. That is the deal, and it is why SDK.ac can stay free without a "Pro" tier.
Our Mission
SDK.ac exists to make working with AI faster and less frustrating for people who write, code, translate, and publish for a living. We believe everyday AI utilities should be free, instant, mobile-friendly, and private by default. Whether you are drafting an email on a train, building an image prompt for a client mock-up, or trying to understand a block of unfamiliar code, you should get to a useful result in seconds — not after a signup flow.
We measure ourselves on three numbers: time-to-result (target: under three seconds from cold page load to usable output), clicks-to-result (target: as few as the task allows), and bytes of your text stored on our servers (target: zero). Every design decision on this site is downstream of those three numbers.
Long-term, the mission is bigger than the current catalogue. Prompting well is quickly becoming a basic literacy, like search queries were twenty years ago. We want SDK.ac to be the place a colleague recommends when you ask "is there a tool that helps with that?" — and we want you to feel zero regret when you click the link.
Who We Are
SDK.ac is operated by SDK Co., Ltd., a Korean software company founded in 2024 that builds free online utilities and developer-focused tools. Our team has shipped consumer and developer web products used by millions of people, and we apply the same standards for UX, accuracy, and speed to every tool on this site.
Beyond SDK.ac, the same team operates SDK.is (developer utilities), JavaScript.ac (interactive JavaScript learning), 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
- AI tools, prompt utilities, free web tools
- 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.ac
SDK.ac currently ships eight AI tools. All of them are free, none of them require an account, and all of them process your input on your own device.
AI Translator
Builds a precise, context-aware translation prompt for any pair of twelve major languages. Instead of a generic "translate this," you get a prompt engineered to preserve tone, register, and formatting — which produces dramatically better output from ChatGPT, Claude, or Gemini than a bare request.
Text Summarizer
Condenses long articles, reports, or transcripts into their key sentences. The extraction runs entirely in your browser — your document is never uploaded — making it safe for internal memos and confidential drafts.
AI Prompt Generator
Turns a rough idea ("write a product launch post") into a structured prompt with role, context, constraints, and output format. The difference between a lazy prompt and a structured one is usually the difference between a rewrite and a keeper.
Image Prompt Builder
Assembles detailed prompts for Midjourney, DALL·E, and Stable Diffusion from your subject, style, lighting, composition, and mood choices. Great for designers who know what they want visually but not how image models want to hear it.
Code Explainer
Wraps any code snippet in an explanation prompt tuned to your experience level — from "explain like I am new to programming" to "give me a senior-level review." Supports all common languages and never transmits your code anywhere.
Email Writer
Generates professional email prompts from a purpose, tone, and a few bullet points. Covers follow-ups, cold outreach, apologies, negotiations, and the other emails everyone rewrites five times before sending.
Hashtag Generator
Produces platform-appropriate hashtag prompts for Instagram, X, TikTok, and LinkedIn from your topic and audience, balancing reach tags with niche tags instead of dumping thirty generic ones.
Writing Assistant
One-click prompts to improve, shorten, expand, formalise, or simplify any passage of text. Ideal for polishing a paragraph without re-explaining the whole context to an AI chat from scratch.
Our Principles
Free Forever
No paywalls, no premium tier, no generation credits. Ads keep the tools free for everyone.
Your Text Stays Yours
Tool inputs are processed on your device. We never store, read, or train on what you type.
No Login, Ever
No account, no signup, no email capture. Open the page and start working.
Fast by Default
Sub-second loads on Cloudflare’s global edge network, on desktop and mobile alike.
Honest About AI
AI output can be wrong. We say so plainly, on every page where it matters.
No Dark Patterns
No fake countdowns, no "2 free uses left," no roach-motel cookie banners.
Technology Stack
Every piece of the stack was chosen to optimise load speed, reliability, and long-term maintainability for a small team.
The frontend is built with SvelteKit and TypeScript, styled with Tailwind CSS, and deployed to Cloudflare Pages. There is no traditional backend: pages are rendered at the edge, tool logic runs in your browser, and preferences (theme, language) live in your own localStorage. Where a tool produces a prompt for an external AI assistant, you carry that prompt to the assistant yourself — we never proxy your text through our infrastructure.
This architecture has practical consequences for you. First, time-to-interactive is measured in tens of milliseconds, not seconds. Second, there is no server database of user text that could leak, be subpoenaed, or be sold — because it does not exist. Third, our infrastructure costs are low enough that SDK.ac can stay free indefinitely without ever introducing a paid tier.
AI Limitations, Honestly
We build tools for working with AI, so we owe you plain talk about what AI cannot do. Large language models generate plausible text; they do not guarantee true text. They hallucinate facts, invent citations, mistranslate idioms, produce code that compiles but is subtly wrong, and write with total confidence in every one of those failure modes. A well-structured prompt — which is what our tools help you build — meaningfully improves output quality, but it does not eliminate these risks.
Our position is simple: AI output is a draft, not a deliverable. Verify translations with a native speaker before publishing. Run and test generated code before shipping it. Fact-check summaries against the source document when the stakes are real. Nothing produced with the help of SDK.ac constitutes professional, legal, medical, or financial advice, and the responsibility for reviewing and using AI output rests with you. We would rather say this clearly on our About page than bury it in a footnote.
How We Handle Your Text
Everything you type into a SDK.ac tool — text to summarize, code to explain, email points to draft — is processed on your device. It is not transmitted to our servers, not logged, not stored, and not used to train any model. When a tool generates a prompt for an external AI assistant, that prompt exists only in your browser until you choose to copy it and paste it somewhere else. What happens after you paste it into a third-party AI service is governed by that service's privacy policy, so choose your assistant accordingly for sensitive material.
The only data we collect is standard aggregated analytics (page views, country, device type) and the advertising cookies described in our Privacy Policy, which you can refuse. We never sell or share personal data. If our advertising provider changes its consent rules, we will update our consent handling immediately and note the change on the Privacy Policy page.
Contact Us
Have questions, suggestions, or feedback? We read every message.
- General questions and feedback: contact@sdk.ac
- Bug reports: please include the tool, your browser and OS, and steps to reproduce.
- Tool suggestions: tell us which AI task you wish had a one-button tool — real use cases move our roadmap.
- Business, partnership, and advertising: include "Business" in your subject line.
- Privacy requests and legal notices: include "Legal" in your subject line.
Legal & Operator Information
SDK.ac is operated by SDK Co., Ltd., a Korean corporation registered with the competent authorities of the Republic of Korea (business registration 871-81-03242, e-commerce registration 2024-고양일산서-1820).