10 Free Browser-Based Tools Every Backend Developer Should Bookmark
Source: Dev.to
As a backend developer, I spend a surprising amount of time on small but repetitive tasks — converting a subnet mask, decoding a JWT, formatting a SQL query, or generating test data before a demo. These aren’t hard problems, but they slow you down when you have to hunt for the right tool every time.
Tools
1. IP / Subnet Calculator
Handy Dev Tools — IP Calculator
Paste a CIDR like 192.168.1.0/24 and instantly get the network address, broadcast address, wildcard mask, usable host range, and binary/hex notation. Pair it with the Subnet Split tool to divide a network into equal subnets by count, host requirement, or prefix length — results exportable as CSV. Useful when designing VPC address spaces or writing firewall rules and you need to double‑check your math fast.
2. CloudFront Signed URL Generator
Handy Dev Tools — CloudFront Signer
Generates AWS CloudFront signed URLs entirely in the browser using RSA‑SHA1. Supports both Canned Policy (expiration only) and Custom Policy (IP restriction, start time, wildcard resource patterns). Your private key never leaves the browser — it’s handled in memory only. Handy for quickly testing signed URL behavior before wiring it into your application code.
3. JWT Decoder
Paste a JWT and immediately see the decoded header, payload, and signature verification status. It works exactly as expected — no reason to switch if you’re already using it.
4. S3 Path Formatter
Handy Dev Tools — S3 Path Formatter
Converts between every S3 format in one place: s3:// URI, ARN, path‑style HTTP URL, virtual‑hosted URL, CloudFront URL, and AWS Console URL. Paste any format, get all the others instantly. Saves the mental overhead of remembering which format the AWS CLI, SDK, IAM policy, or CloudFront origin config expects.
5. JSON / YAML / SQL Formatter
Fast, in‑browser formatters for JSON, YAML, SQL (with dialect support), XML, GraphQL, and Markdown. For SQL, the formatter preserves semantics while normalizing indentation and keyword casing — useful before committing a migration file.
6. Regex Tester
The best dedicated regex tool available. Supports PCRE, JavaScript, Python, Go, and Java with detailed match explanations and a built‑in library of saved expressions. Ideal for working with complex patterns.
7. Test Data Generator
Handy Dev Tools — Test Data Generator
Generate up to 10,000 rows of realistic dummy data across 50+ field types: UUIDs, names, addresses, phone numbers, IP addresses, JWT tokens, API keys, credit card numbers, Japanese era dates, and more. Output formats include JSON, CSV, SQL INSERT, and Laravel Seeder. The Laravel Seeder output can be pasted directly into a DatabaseSeeder.php.
8. Hash Generator
Handy Dev Tools — Hash Generator
Supports MD5, SHA‑1, SHA‑256/512, SHA‑3, bcrypt, scrypt, Argon2, HMAC variants, and CRC32—for both text and file input. All hashing runs client‑side, which matters when you’re working with sensitive data.
9. cURL to Code Converter
Paste a cURL command and get equivalent code in Python (requests), JavaScript (fetch/axios), PHP, Go, Ruby, and more. Invaluable when you’re copying a request from browser DevTools and need to reproduce it in your backend code.
10. HTTP Status Code Search
Handy Dev Tools — HTTP Status Search
Search by code number or keyword (e.g., “redirect”, “auth”, “rate”) and get the status name, meaning, common causes, and when to use it. Works offline—the database is bundled in the page. Quick reference when deciding between 400 vs 422, or 301 vs 307.
Wrapping Up
Most of these tools do one thing well and stay out of your way. The ones I reach for most often are the subnet calculator, S3 path formatter, and test data generator—they solve problems that are tedious enough to slow down a workflow but not complex enough to warrant writing custom scripts.
If you know a tool that belongs on this list, feel free to share it in the comments.
Tools 1, 2, 4, 5, 7, 8, 10 are from Handy Dev Tools — a free, open toolkit with 69+ browser‑based tools available in 7 languages.