Developer Tools

Developer Tools gathers the browser-based utilities engineers reach for while writing, debugging, and shipping code, regex testers, crontab generators, curl-to-code translators, a Docker Compose scaffolder, diff checkers, and Markdown converters. A backend engineer mid-sprint can validate a regex against 200 sample strings, convert a curl command from Postman into Python requests, and verify that 0 */6 * * * runs every six hours, all in one tab. The category ships 39 utilities covering the reference topics developers hit weekly: regex, cron, curl, Markdown, and network math. Each runs client-side, no account, no paste limit, no data leaving the browser.
What you can do with Developer Tools

Test and generate regex patterns, validate a pattern against sample input with the Regex Tester, or build one from examples with the Regex Generator from Text.
Translate curl commands into code, convert a curl call to fetch, Python requests, or PHP cURL without rewriting flags by hand.
Schedule cron jobs, build expressions with the Crontab Generator and preview the next runs with the Cron Parser.

Pick Developer Tools when the input is code, a config fragment, or a regex pattern and the output is another piece of code or a live verification. For byte-level encoding (base64, URL encoding, hashing), the right category is Encoding Tools. For JSON, CSV, XML, or YAML reshaping, flatten, diff, or infer a schema, Data Tools operates at the document level. Character-level text work like case changes and slug conversion sits in Text Tools.
The Developer Tools toolkit

Tool
What it does
When to use

Regex Tester
Matches a regex against test strings with live highlighting
Debugging a pattern before committing it to production

Regex Generator from Text
Infers a regex from input/output examples
Extracting order IDs or dates from a log sample

Regex Generator
Builds common regex patterns from a checklist
Matching emails, URLs, IPs, or phone numbers quickly

Regex Cheat Sheet
Reference card for syntax, quantifiers, and lookarounds
Looking up b vs B mid-review

Crontab Generator
Builds a cron expression from plain-English intervals
Scheduling a 2 a.m. weekly backup job

Cron Parser
Lists the next N firing times for a cron expression
Verifying 30 */4 * * 1-5 before deploying it

curl to fetch
Converts a curl command to a JavaScript fetch call
Porting an API debugging session from Postman to a web app

curl to Python requests
Converts a curl command to a requests call
Turning a one-liner test into a Python script

curl to PHP cURL
Converts a curl command to PHP curl_* calls
Adding a remote API call to a legacy WordPress plugin

Docker Compose Generator
Scaffolds a docker-compose.yml from service fields
Standing up a Postgres + Redis + app stack on a new laptop

Diff Checker
Compares two blocks of text and highlights changes
Reviewing a config drift between staging and production

JavaScript Minifier
Strips whitespace and renames locals in JS
Shrinking a 40 KB script before pasting it into a CMS

HTML to Markdown
Converts HTML into CommonMark Markdown
Importing a scraped blog post into a Jekyll or Hugo site

IP Subnet Calculator
Computes network, broadcast, and host range from a CIDR
Planning a /24 split for a new VPC

Regex utilities cover writing, testing, and debugging patterns. The Regex Cheat Sheet is for syntax lookup, the Regex Generator from Text infers a pattern from input/output examples, and the Regex Tester confirms the match before you paste it into code.
Scheduling and HTTP translators solve the same small-text-must-be-exact problem. The Crontab Generator writes the expression; the Cron Parser reads it back with the next five runs. The three curl converters, to fetch, to Python requests, and to PHP cURL, port a call into another language without rewriting flags by hand.
Format and code converters round out the set. The Docker Compose Generator scaffolds a multi-service stack, the Diff Checker highlights line-level changes, the JavaScript Minifier strips a file for deployment, HTML to Markdown flattens HTML into CommonMark, and the IP Subnet Calculator turns a CIDR into network, broadcast, and host-range values.
How to choose the right Developer Tool

If you’re debugging an existing pattern that needs to match 20 sample strings → Regex Tester.
If you need a cron expression for an off-hours backup → build it in the Crontab Generator and verify with the Cron Parser.
If you captured a request with curl -H ... -d ... and want it in a Python test → curl to Python requests.
If you’re planning a VPC split from a CIDR → IP Subnet Calculator.
If you’re comparing two config files line-by-line without opening git → Diff Checker.

The trade-off that matters is convenience vs. reproducibility. Browser tools are faster for one-offs, test a regex, generate a cron expression, or convert a curl call in 30 seconds. For anything that ends up in CI, wire the equivalent logic into your repo: pytest fixtures for regex tests, a checked-in docker-compose.yml, a crontab under version control. The tools here are the scratch pad, your codebase is the source of truth.
Frequently asked questions
Are these developer tools free to use?
Yes. Every tool runs free in your browser with no account, no rate limit, and no paid tier. Computation happens client-side, so a private curl command or an internal regex stays off our servers. The full set is 39 utilities across regex, cron, curl, Docker Compose, and network math.
Do my inputs leave the browser?
No. Every tool in this category is client-side JavaScript, the regex engine, the curl parser, the cron clock, and the diff algorithm run in your tab. That matters when you paste a production connection string into the Diff Checker or an API token into curl to fetch. Nothing is logged and nothing is posted to a server.
Which regex flavor does the Regex Tester use?
The Regex Tester runs JavaScript’s built-in RegExp engine, ECMAScript flavor. That covers the standard metacharacters, character classes, quantifiers, alternation, groups, lookaheads, and named groups ((?<name>...)). For PCRE-only features like recursive patterns and conditional groups, reach for a PCRE-specific tester.
What cron syntax does the Crontab Generator support?
The Crontab Generator produces standard 5-field Unix cron expressions: minute, hour, day-of-month, month, day-of-week. Ranges (1-5), lists (1,3,5), step values (*/15), and names (MON, JAN) all parse. Quartz-style 6- or 7-field expressions are not generated. Paste the output into the Cron Parser for the next five fire times.
How do the curl converters handle authentication headers?
Headers pass through verbatim. If your curl command contains -H "Authorization: Bearer ..." or -u user:pass, the output from curl to fetch, curl to Python requests, or curl to PHP cURL keeps the equivalent header or auth tuple. Scrub secrets before pasting into chat, docs, or a shared branch.
Can I use these tools without an internet connection?
After a tool’s page loads once, most keep running offline for that session, the logic is client-side. Close the tab and you’ll need a connection to reopen. For a repeatable offline workflow, bookmark the five or six utilities you use most.
For byte-level transforms like base64, URL encoding, or hashing, head to Encoding Tools. For JSON, CSV, XML, or YAML reshaping, Data Tools is the right stop. For case changes, slug conversion, and find-and-replace, Text Tools sits alongside this page.