Dev Security: JSON & Tokens (2026)

Every developer spends hours on the same tiny tasks. Fixing a broken JSON payload from ChatGPT. Converting a cURL command from API docs into working fetch code. Testing a regex that keeps failing. Counting tokens to estimate an LLM API bill.

This guide is the complete developer toolbox for 2026. Every tool runs in your browser, processes on your device, and never uploads your code, secrets, or API keys. No signup, no rate limits, no watermarks.

By the end, you will have a browser bookmark folder of developer tools that replaces half a dozen SaaS subscriptions and gives you more privacy in the process.

1. JSON: fix broken payloads from AI models

ChatGPT, Claude, and every other LLM regularly return broken JSON. Trailing commas, markdown fences, missing quotes, unescaped newlines. If your app calls JSON.parse() on the raw response, it crashes.

The JSON AI Fixer strips markdown, repairs trailing commas, escapes bad characters, and outputs clean, valid JSON. It runs the jsonrepair library entirely in your browser.

Once the JSON is clean, use the JSON to Code tool to auto-generate TypeScript interfaces, Go structs, or Rust types. Saves 10-30 minutes per new API integration.

2. Tokens: count before you pay

Every OpenAI, Anthropic, or Google AI API call is billed by tokens. A token is roughly 4 characters or 0.75 words. If you send a large system prompt 100,000 times per month, the cost compounds fast.

The LLM Token Counter uses the exact same Tiktoken library that OpenAI uses, so the count is accurate to the token. Use it to estimate costs, compare prompt sizes, and reduce wasted tokens.

The Prompt Sanitizer removes invisible whitespace, trailing spaces, tabs, and excess newlines that waste tokens without adding value. It typically cuts 5-15 percent of a system prompt.

3. Regex: test before you ship

A bad regex can bring down your API. Catastrophic backtracking, unexpected greedy matches, subtle off-by-one errors. The Regex Tester shows live highlighting as you type and reports execution time, so you can spot performance issues before they hit production.

Common patterns you can test instantly:

Email (basic): ^[^\s@]+@[^\s@]+\.[^\s@]+$

Phone (US): ^\+?1?[-.\s]?\(?[0-9]{3}\)?[-.\s]?[0-9]{3}[-.\s]?[0-9]{4}$

UUID v4: ^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$

URL: ^https?:\/\/[^\s/$.?#].[^\s]*$

4. cURL: convert docs to real code

You copy a cURL command from API documentation. It is 300 characters with escaped quotes, JSON payloads, and headers. Now you have to manually translate it into JavaScript.

The cURL to Fetch tool parses the cURL command and outputs clean fetch or axios code, with the body properly stringified, headers formatted, and method inferred correctly.

5. JWT: decode without trusting the source

JSON Web Tokens are opaque strings. To debug auth issues, you need to see the header, payload, and expiration. The JWT Decoder splits the token and shows the decoded claims without ever making a network request.

6. Minify: faster sites, better SEO

Every byte of whitespace, comment, and unused variable in your CSS and JS costs real milliseconds on page load. Google treats page speed as a ranking factor. Minify before you deploy.

Do not minify once and forget. Add minification to your build pipeline. If you are using raw HTML/CSS/JS without a build step, minify before every deploy with these browser tools.

7. Base64: encode and decode safely

Base64 appears everywhere: JWT tokens, data URLs, email attachments, HTTP Basic Auth. The Base64 Encoder decodes and encodes text and small files locally. Perfect for testing API auth headers or decoding attachments.

8. Hash: verify integrity

Need to verify a downloaded file matches its SHA-256 checksum? The Hash Generator computes MD5, SHA-1, SHA-256, and SHA-512 for any file or text, entirely on your device.

9. UUID: generate time-sortable IDs

If you are still using UUID v4 for database primary keys, you are hurting performance. Random IDs cause B-Tree index fragmentation, slowing down inserts and queries. UUID v7 and ULIDs are time-sortable — new records append to the end of the index.

10. Epoch: convert Unix timestamps

A database timestamp of 1729998000 — what day is that? The Epoch Converter converts Unix timestamps to local time, UTC, and ISO 8601, and detects whether the timestamp is in seconds or milliseconds.

The developer workflow that saves hours

Here is the pattern experienced developers use to save hours per week:

1. When getting AI output: paste into JSON AI Fixer, then JSON to Code. Get typed objects in seconds.
2. Before making LLM API calls: count tokens with Token Counter. Sanitize prompts. Know your cost.
3. When debugging auth: decode JWT, count payload size, verify signature server-side.
4. Before deploying code: minify CSS/JS/HTML. Regenerate thumbnails with Image Compressor.
5. When building new tables: generate UUID v7 (not v4). Time-sortable IDs are 2-3x faster for inserts.
6. When reading logs: Epoch Converter for Unix timestamps. JWT Decoder for tokens.

Why on-device tools matter for developers

When you paste API keys, database schemas, or JWT tokens into a random online tool, you are trusting that service with your application security. Most free tools upload your data to a server, log it, and sometimes monetize it.

Every tool in this guide runs on-device using JavaScript and WebAssembly. Open the Network tab in developer tools while using them: you will see no upload requests. Your data stays in your browser memory and is discarded when you close the tab.