MonkKit — 106 Free Developer Tools in One Place
I was tired of bouncing between a dozen different sites just to format JSON or decode a JWT. One tab for a JSON formatter. Another for a Base64 decoder. Another for a DNS lookup. Another for an SPF validator. Browser full of bookmarks, half of them plastered with ads, most requiring an account to do anything useful.
So I built MonkKit — a single place for all of them. 106 free developer tools across 10 categories. No login required. No ads. Everything runs in your browser or through a REST API.
The Problem
As a DevOps engineer I reach for the same set of tools constantly. Format a JSON response from an API. Check DMARC and SPF records for a domain. Decode a JWT. Calculate a subnet mask. Convert a Unix timestamp. Inspect an SSL certificate. These are five-second tasks that somehow take two minutes because you have to remember which website does which thing, wait for it to load, dismiss the cookie banner, and find the right input field.
The tools that do exist are scattered. A lot are outdated. Many are wrapped in so much advertising they are actively unpleasant to use. Some require sign-up for basic operations. None of them work offline.
MonkKit is the answer I wanted: every tool I actually reach for, in one fast, clean interface, with a consistent API for when I need to automate.
What MonkKit Is
MonkKit is a free web-based developer toolbox. 106 tools across 10 categories. Every tool is available in the browser with no account needed. The same tools are also available via REST API — useful for CI/CD pipelines, scripts, and automation.
The categories cover the full stack of things a developer or DevOps engineer actually does day to day.
The 10 Tool Categories
JSON Tools — 31 tools
JSON is everywhere. Validate it, format it, minify it, compare two blobs, convert it to YAML, CSV, XML, or TypeScript interfaces. Extract specific fields with JSONPath. Sort keys. Flatten nested structures. The JSON category is the most comprehensive section — 31 tools covering every JSON operation I have ever needed.
Typical uses:
- Format a compressed API response so it is readable
- Validate a config file before deploying
- Convert a JSON payload to a TypeScript interface
- Diff two JSON objects to see what changed between API versions
Network — 16 tools
DNS lookups, WHOIS queries, subnet calculators, and network diagnostics. Indispensable for infrastructure work.
Look up A, AAAA, MX, TXT, CNAME, NS, and SOA records for any domain. Run a WHOIS query. Calculate subnets and CIDR ranges. Check whether a port is open. Reverse-lookup an IP address.
These are the tools I use daily when debugging DNS propagation, setting up new infrastructure, or troubleshooting connectivity issues.
Email & DNS — 11 tools
Email deliverability is a rabbit hole. SPF misconfigurations, missing DKIM records, incorrect DMARC policies — all of them cause your emails to land in spam silently. The Email & DNS category gives you tools to check all of it.
- MX lookup — see which mail servers a domain uses
- SPF checker — validate SPF records and trace
include:chains - DMARC lookup — check DMARC policy and alignment settings
- DKIM lookup — verify DKIM public keys are published correctly
- Email header analyser — paste a raw email header and see the delivery path, timestamps, and spam scores
If you manage email for a domain and wonder why messages are going to spam, start here.
Encoding & Hashing — 9 tools
Base64 encode and decode. URL encode and decode. Hex encode. HTML entity encode. Generate MD5, SHA-1, SHA-256, and SHA-512 hashes.
These are the tools that come up when debugging authentication headers, API request signing, URL construction, and cookie values.
Cryptography — 8 tools
Classical ciphers (Caesar, ROT13, Vigenère), XOR operations, and encryption utilities. Useful for CTF challenges, security research, and understanding how ciphers work at a foundational level.
Certificates — 6 tools
Decode PEM certificates to see subject, issuer, SANs, expiry, and key details. Generate self-signed certificates for local development. Convert between PEM, DER, and PKCS12 formats. Check whether a certificate chain is valid.
Certificate debugging used to mean running openssl x509 -in cert.pem -text -noout and reading a wall of output. The certificate tools format that same information clearly and highlight what matters.
Images — 12 tools
Resize, crop, convert, compress, and apply filters to images — entirely in the browser. No upload to a server, no privacy concerns. The image processing runs client-side using the browser’s Canvas API.
Convert PNG to WebP, compress a JPEG for a web page, resize a screenshot to a specific dimension, or apply a greyscale filter. All without installing ImageMagick or opening Photoshop.
Text — 8 tools
String manipulation, transformation, and analysis. Convert case (camelCase, snake_case, PascalCase, kebab-case). Count words and characters. Sort lines. Remove duplicates. Escape and unescape strings. Diff two text blocks.
Small things that come up constantly in scripting and code review.
Generators — 3 tools
Generate QR codes and barcodes from any text or URL. Useful for product labels, documentation, and sharing URLs in printed materials.
Date / Time — 2 tools
Convert Unix timestamps to human-readable dates and back. Format dates across timezones. Useful when reading server logs, debugging API responses, and working with epoch timestamps in databases.
REST API
Every tool in MonkKit is also available via REST API. The same JSON formatter you use in the browser is callable from a script, a CI/CD pipeline, or a pre-commit hook.
Get an API key from the site (free), and call any tool endpoint with a POST request:
curl -X POST https://tools.devops-monk.com/api/json/format \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"input": "{\"name\":\"abhay\",\"role\":\"devops\"}"}'
Useful for:
- Validating JSON config files in a CI pipeline before deployment
- Checking DNS records as part of an infrastructure test
- Automating certificate expiry checks
- Integrating email health checks into a monitoring workflow
Tech Stack
MonkKit is built with:
- Next.js + TypeScript — frontend and API routes
- Kubernetes — container orchestration for the backend services
- Terraform — infrastructure provisioned as code
- CI/CD pipeline — automated builds and deployments on every push
The image processing tools run entirely client-side — no data leaves your browser. Network and DNS tools run server-side against the target host. API requests are rate-limited per key.
Why Free
MonkKit is a side project. I built it for myself and decided to open it up because the tooling landscape is worse than it should be. The plan is to keep everything free. If it is useful and you want to support the hosting costs, there is a Buy Me a Coffee link on the site — but it is genuinely optional.
Try It
tools.devops-monk.com — no account, no ads, no friction.
Browse by category, search for the tool you need, or grab an API key if you want to automate. If there is a tool missing that you reach for regularly, open an issue or reach out — the list is already at 106 and growing.
