Free online developer tools
Free online developer tools for security, networking, DevOps, data, SEO and everyday development tasks.
12 tools available now. No account needed.
Featured tools
A good place to start. Every tool here is live and free to use.
Log Sanitizer
Mask secrets, tokens, and PII in logs before you share them.
JSON Formatter
Format, validate, beautify, minify, and explore JSON instantly.
CIDR Calculator
Calculate subnet info from an IPv4 CIDR block.
CSP Analyzer
Analyze Content Security Policy headers, detect configuration issues, explain directives and sources, and generate safer CSP recommendations.
HTTP Security Headers Analyzer
Analyze HTTP response headers for security configuration issues.
Redirect Chain Analyzer
Analyze URL redirects, detect redirect chains and loops, and inspect HTTP status behavior.
Browse by category
Tools grouped by the kind of job they help with.
Why DevCraftKit
Results you can understand
Findings come with an explanation of what they mean and how to fix them, not just a pass or fail.
Privacy stated plainly
Each tool says whether your input stays in the browser. No account is needed to use any of them.
Honest about limits
Every analyzer lists what it cannot see, so you know when to verify a result another way.
Guides next to the tools
Short explainers on the concepts behind each tool, written to answer the question rather than pad a page.
What developer utilities are for
Developer utilities are small, single-purpose tools for chores that come up again and again: reformatting a block of data, working out a number, or checking a piece of configuration. They are not a framework or a platform. You open one for half a minute, get an answer, and go back to what you were doing.
The problems they solve are familiar. A log has to go into a support ticket, but it contains email addresses, tokens and internal IP addresses. An API response arrives as one unreadable line. A new subnet might overlap an existing one. A site starts blocking its own scripts after a Content-Security-Policy is added, or search traffic drops after a migration because every old URL now takes three redirects to resolve.
Running these tools in the browser means there is nothing to install, they behave the same on any operating system, and a result is a link away from a colleague. The trade-off is trust: a web page can only be as private as what it does with your input.
Why local processing matters
"Processed locally" means the page's code runs on your device and your input is not sent to a server. That matters most for logs, headers, tokens and configuration, which often hold things you would not post publicly. DevCraftKit tools work this way wherever the task allows it, and a tool that has to contact something, such as the Redirect Chain Analyzer in URL mode or the Open Graph & Social Preview Analyzer, says so beside its input. Read the Privacy Policy for the full picture, and keep real secrets out of any web page you do not need to paste them into.
Common workflows
Share a log safely
Mask emails, tokens and IP addresses in a log before it goes into a ticket or chat, and tidy a minified request body so the problem is easy to see.
Check a site after a change
After a migration or a server change, look for redirect chains, review the Apache rules behind them, then check the response headers and the Content-Security-Policy.
Check how a link will look when shared
Check the Open Graph and Twitter/X Card tags, the social image and the canonical URL of a public page, and make sure the link does not bounce through extra redirects first.
Investigate a suspicious email
Read the delivery route and the SPF, DKIM and DMARC results in a message's raw headers, and mask addresses and IPs before you share them with anyone else.
Plan a network
Work out how many addresses a block holds, where it starts and ends, and whether two ranges overlap before you create a VPC or carve up subnets.
Featured guides
Practical explanations of the concepts behind the tools.
What Is CIDR? A Complete Guide to Classless Inter-Domain Routing
CIDR notation packs an IP address and its network size into one compact string. Here's exactly what it means and how to read it.
Updated
Understanding IPv4 Subnetting: A Practical Guide
Subnetting is how one IP range gets divided into smaller, purpose-built networks. Here's a practical walkthrough with real examples.
Updated
What Is Log Sanitization? Why It Matters and How to Do It
Logs capture more than errors - they capture whatever was nearby when something went wrong, including data that should never leave your system.
Updated
Recently added tools
Image Metadata & AI Provenance Cleaner
Inspect image metadata, check supported AI provenance information, and remove hidden metadata locally.
Added October 14, 2026
JWT Decoder & Inspector
Decode a JWT, inspect its claims and expiry, and review potential security issues locally.
Added October 12, 2026
Cron Builder
Build, validate and explain cron expressions, preview run times by timezone, and check dialect compatibility.
Added October 10, 2026
Privacy and local processing
Most tools analyse what you paste inside your browser, so it is not sent to DevCraftKit. There are no accounts. Two tools make requests: the Redirect Chain Analyzer's URL mode contacts the address you type from your browser, and the Open Graph & Social Preview Analyzer sends the public URL you enter to DevCraftKit's server so it can fetch the page. Each says so where you enter it. See the Privacy Policy for what is stored, which third parties are involved and how advertising works.
Enjoying DevCraftKit?
If these free developer tools save you time, consider buying me a byte. Your support helps keep DevCraftKit free and growing.
Frequently asked questions
- What is DevCraftKit?
- DevCraftKit is a collection of free online developer tools for security, networking, DevOps and data. Each tool is paired with plain-language explanations, examples and guides, so you can understand a result as well as get it.
- Are the tools free, and do I need an account?
- Every live tool is free to use, and no account or sign-up is needed. Nothing is locked behind support.
- Is what I paste into a tool uploaded?
- Most tools analyse your input in your browser, so the text is not sent to DevCraftKit. The exceptions are the URL mode of the Redirect Chain Analyzer, where your browser requests the address you enter, and the Open Graph & Social Preview Analyzer, which sends the public URL you enter to DevCraftKit's server so that the page can be fetched. Each tool page says how it handles input, and the Privacy Policy has the details. As a general habit, avoid pasting real secrets into any web page unless you need to.
- How is DevCraftKit supported?
- Through optional donations via the Buy me a byte link, and it may show clearly labelled advertising. Neither affects how the tools work.
- Which tools are available, and what is coming soon?
- The tool directory shows every tool with its status. Tools marked Coming soon are planned and not available yet, and they are clearly labelled as such.
- Who builds DevCraftKit?
- DevCraftKit is built and maintained independently by one developer. You can report a mistake or suggest a tool from the Contact page.