All tools

Developer tools directory

Search 245 Formalint tools and guides for formatting payloads, cleaning code, decoding tokens, debugging APIs, checking databases and reviewing runtime evidence.

Developer workspace

A local-first multi-tool workstation for active debugging

Formatters

Payload, config and code cleanup

Inspectors

Debug and inspect developer strings

API Debugging ChecklistTrack request identity, auth, payload, logs, retries and final fix notes. curl API Debugging CheatsheetCopy curl commands for headers, JSON POST, auth, timing, redirects, TLS and CORS preflight. OAuth JWT Debugging ChecklistSeparate 401, 403, bearer tokens, scopes, issuer, audience, expiration and refresh-token failures. OpenAPI Contract ChecklistReview paths, operations, parameters, request bodies, responses, schemas and auth contracts. Webhook Debugging GuideDebug webhook deliveries, signatures, retries, idempotency, raw body handling and queue handoff. API Pagination DebuggingInspect Link headers, page size, cursors, offsets, missing results and duplicate rows. API Idempotency Retry GuideDesign safe retries, idempotency keys, duplicate POST handling, timeout recovery and backoff. GraphQL API DebuggingDebug GraphQL queries, variables, operation names, error paths, partial data and HTTP behavior. Cookie SameSite DebuggingInspect Secure, HttpOnly, SameSite, CORS credentials and session cookie failures. CORS Debugging GuideDebug Access-Control-Allow-Origin, OPTIONS preflight, credentials, Vary Origin and browser failures. API Rate Limit DebuggingInspect 429 responses, Retry-After, RateLimit headers, quotas and client backoff behavior. HTTP Cache-Control GuideChoose max-age, no-cache, no-store, immutable and CDN cache behavior safely. HTTP Security Headers ChecklistCheck CSP, HSTS, nosniff, frame protection, referrer policy and permissions policy. HTTP Status CodesSearch response codes and read practical API debugging notes. HTTP Headers ReferenceSearch request, response, cache, CORS and security headers. Regex MatcherUnderstand regex matching, parser behavior, flags and capture groups before testing. Regex TesterTest patterns, flags, matches, indexes and capture groups. Regex ExamplesReview practical patterns before testing them in the matcher. Email Regex ValidatorUse a practical JavaScript email validation pattern with realistic test cases. URL Regex ValidatorCheck HTTP and HTTPS link shapes before using a real URL parser. UUID v4 RegexValidate UUID version and variant characters for API identifiers. Date Regex ValidatorCheck YYYY-MM-DD strings and learn where calendar parsing is still needed. Regex Log ParserCapture timestamps, log levels and messages from semi-structured logs. JWT DecoderDecode headers, payload claims and expiration timestamps. Timestamp ConverterConvert Unix seconds, milliseconds and ISO date values. Cron ParserExplain cron expressions and preview upcoming run times. Email Regex JavaScriptPractical email regex JavaScript guide with realistic validation rules, examples, edge cases and safe production advice. JavaScript Regex CheatsheetJavaScript regex cheatsheet for flags, anchors, groups, character classes, quantifiers, replacement and validation patterns. Lookahead LookbehindRegex lookahead and lookbehind guide for positive assertions, negative assertions, browser support thinking and safer examples. Regex ReplaceRegex replace guide for JavaScript string cleanup, capture groups, named groups, whitespace normalization and safe migrations. Regex PerformanceRegex performance guide for slow patterns, backtracking risk, large logs, input limits and safer parser choices. XML Schema XSDXML Schema XSD guide for validating XML structure, elements, attributes, namespaces and integration contracts. XML to JSON GuideXML to JSON conversion guide for attributes, arrays, namespaces, text nodes and safe API migration notes. YAML Lint ChecklistYAML lint checklist for indentation, tabs, anchors, quoted strings, booleans and CI configuration review.

Converters

Encode, generate and transform values

Guides

Context for safer, better tool usage

Developer GuidesRead original Formalint guides for formatting, validation and safe sample handling. Complete Regex GuideLearn regex fundamentals before copying validation patterns into code. JSON vs XML vs YAMLCompare data formats before choosing a parser, linter or formatter. API Debugging HandbookDebug requests with status codes, headers, payloads, logs and retries. curl API Debugging CheatsheetUse repeatable command-line checks when a browser, proxy or API client behaves differently. OAuth JWT Debugging ChecklistUse token claims and scope evidence before guessing why an API returned 401 or 403. OpenAPI Contract ChecklistKeep API documentation, schemas, generated clients and debugging notes aligned. Webhook Debugging GuideVerify delivery, signature, idempotency and retry behavior for event-driven integrations. API Pagination DebuggingDebug missing results, duplicate rows, unstable exports and client pagination loops. API Idempotency Retry GuidePlan duplicate-safe POST requests, timeout recovery, retry headers and client backoff. GraphQL API DebuggingSeparate query syntax, variable shape, resolver errors, partial data and transport failures. Cookie SameSite DebuggingUnderstand why login sessions disappear across subdomains, redirects and frontend requests. CORS Debugging GuideUnderstand why curl may succeed while frontend JavaScript still cannot read the response. API Rate Limit DebuggingUnderstand 429, Retry-After, quota headers, backoff and gateway ownership. HTTP Cache-Control GuideReview cache directives before shipping stale assets or caching private API data. HTTP Security Headers ChecklistReview browser security headers before tightening production policy. Developer Data ValidationDesign client, server and integration validation without confusing syntax with meaning. Formatter vs Linter vs ValidatorUnderstand the exact job each developer tool category should handle. API Debugging GuideUse a repeatable process for status codes, payloads, logs and schema checks. Docker Env FilesDocker env file guide for Compose variables, quoting, secrets boundaries, defaults and deployment debugging. Kubernetes Pod DebuggingKubernetes pod debugging guide for Pending, CrashLoopBackOff, ImagePullBackOff, logs, events and kubectl describe evidence. DNS DebuggingDNS debugging guide for A, CNAME, TXT, MX, nameservers, propagation, TTL and domain launch checks. TLS Certificate DebuggingTLS certificate debugging guide for HTTPS failures, redirects, certificate names, expiry, chains and mixed content. Nginx 502 504Nginx 502 and 504 debugging guide for upstream health, proxy timeouts, logs, DNS, TLS and gateway ownership. PowerShell Network DebuggingPowerShell network debugging guide for ping, TCP port tests, DNS, routes, services and Windows API connectivity. Git Merge ConflictsGit merge conflict guide for reading conflict markers, choosing changes, testing the result and finishing merges safely. Git Rebase WorkflowGit rebase workflow guide for updating branches, resolving conflicts, continuing safely and avoiding history surprises. PostgreSQL LocksPostgreSQL lock debugging guide for blocked sessions, pg_stat_activity, pg_locks, transactions and safe incident notes. PostgreSQL IndexesPostgreSQL index debugging guide for EXPLAIN, missing indexes, unused indexes, row estimates and safe query review. MySQL Slow QueriesMySQL slow query debugging guide for slow query log, EXPLAIN, indexes, lock time, rows examined and safer tuning notes. npm Dependency DebuggingNode.js npm dependency debugging guide for package-lock, npm install, npm ci, scripts, engines and module resolution. PHP Composer AutoloadPHP Composer autoload debugging guide for vendor files, namespaces, class maps, optimized autoload and deployment checks. Java Memory DebuggingJava memory debugging guide for heap settings, OutOfMemoryError, container limits, GC logs and JVM runtime evidence. Regex ExamplesLearn when common regex patterns are useful and where they should be reviewed. JSON Schema GuideLearn how generated schemas, required fields and array examples should be reviewed. Safe Online ToolsLearn what not to paste into browser-based utilities. SQL Formatting GuideReview practical formatting patterns for readable SQL.

Admin library

DBA, operating system and runtime references

DBA Admin RoadmapPlan access, backups, restore tests, monitoring, incidents, SQL review and documentation. Terminal Workflow GuideChoose CMD, PowerShell, Git Bash or Linux shell while debugging systems, APIs and databases. Linux Cockpit Server GuideInstall Cockpit, open port 9090 carefully and verify a browser-based server console. Docker Compose DebuggingInspect Compose services, logs, ports, env files, volumes, healthchecks and rebuilds. PostgreSQL DBA ChecklistUse psql commands for identity, sessions, locks, size, vacuum, backups and incidents. MySQL DBA ChecklistUse mysql, mysqladmin and mysqldump checks for processlist, InnoDB, logs and backups. Redis Debugging ChecklistUse redis-cli checks for INFO, memory, clients, slowlog, keyspace and cache incidents. Nginx Reverse Proxy ChecklistCheck config, upstreams, proxy headers, TLS, redirects, logs and API gateway behavior. Windows Admin CommandsInspect Windows services, ports, logs, disks and database hosts with CMD and PowerShell. Linux Admin CommandsInspect Linux services, logs, sockets, storage, packages, users and firewall state. PHP Runtime ChecklistCheck PHP CLI, FPM, Composer, extensions, php.ini, Apache and Nginx runtime evidence. Java Runtime ChecklistCheck JDK, JAVA_HOME, Maven, Gradle, JVM flags and service runtime behavior. Python Runtime ChecklistCheck Python, pip, virtual environments, package paths, FastAPI, Django and worker services. Node.js Runtime ChecklistCheck Node, npm, lockfiles, package scripts, environment variables, ports and PM2. Hardware DiagnosticsConnect CPU, memory, disk, IO and network symptoms to app and database incidents.

API reliability

Production API contracts, retries, signatures and delivery troubleshooting

Lint and cleanup

XML, YAML, SQL and JSON cleanup references

Email validation

Email regex, syntax checks and validation workflows

Community forum

Forum, question templates and safe debugging threads

SEO & indexing

Search Console, sitemap, canonical and AdSense readiness checks

Browser debugging

DevTools, network, Lighthouse and JavaScript evidence

Security & compliance

Policies, secrets, cookies and browser security

CI/CD & release

Builds, tests, releases and rollback evidence

Observability

Logs, health checks, monitoring and reliability signals

Cloud deployment

DNS, HTTPS, static hosting and CDN launch checks

Advanced references

Regex, API, SQL, runtime and operations deep dives

Phone Number Regex ValidationValidate phone-shaped input without pretending regex can prove a reachable number. Password Regex ValidationDesign password checks that help users without creating fragile security theater. IP Address Regex ValidatorCheck IPv4 string shape before using network tools or address parsers. Slug Regex ValidatorKeep public URLs clean, readable and predictable. HEX Color Regex ValidatorCheck color strings before converting them into RGB or HSL. JavaScript Regex match vs testChoose the right JavaScript regex method before trusting a result. JSON Escape and UnescapeRead JSON string escaping without breaking valid payloads. JSON Lines and NDJSONDebug newline-delimited JSON exports without wrapping everything by instinct. API 401 vs 403 DebuggingSeparate missing authentication from denied authorization. API Timeout DebuggingTurn vague timeout reports into ordered evidence. JWT Expiration DebuggingUnderstand token time claims without exposing real credentials. SQL JOIN DebuggingFind why a JOIN returns too many, too few or duplicated rows. SQL WHERE Clause DebuggingStop tiny WHERE mistakes from becoming wrong reports. SQL Injection Prevention ChecklistKeep SQL cleanup separate from SQL injection prevention. PostgreSQL VACUUM and ANALYZERead PostgreSQL maintenance symptoms before tuning blindly. MySQL Index DebuggingUse evidence before adding another index. Redis Memory DebuggingFind Redis memory pressure before deleting keys in a hurry. Docker Container LogsRead container logs without losing service context. Linux journalctl for Developers and DBAsTurn Linux service logs into ordered incident evidence. PowerShell curl vs Invoke-WebRequestAvoid Windows shell surprises while testing APIs. PHP-FPM and Nginx DebuggingFind whether the failure belongs to Nginx, PHP-FPM or application code. Java Thread Dump DebuggingCapture JVM evidence before restarting the service. Python Virtualenv DebuggingFind why Python works in one shell but fails in the service. Node.js Environment Variable DebuggingFind where an environment variable disappears. curl POST JSON RequestBuild repeatable curl POST requests for JSON APIs without losing headers, body shape or auth context. HTTP Request MethodsUnderstand GET, POST, PUT, PATCH, DELETE, HEAD and OPTIONS before debugging API behavior. REST API Error ResponseDesign and debug consistent REST API error responses with status, code, message, details and correlation IDs. API Versioning StrategyPlan URL, header and media-type API versioning so client integrations do not break quietly. Webhook Signature VerificationVerify webhook signatures with raw bodies, timestamps, HMAC secrets and replay protection. OAuth Refresh Token DebuggingDebug refresh-token rotation, expired sessions, revoked grants and frontend retry loops. Regex Extract NumbersExtract integers, decimals, negative values and IDs from text while keeping parsing limits clear. Regex Remove Duplicate LinesClean repeated lines in logs, lists and copied text with regex-aware review notes. Regex Whitespace NormalizationNormalize spaces, tabs, blank lines and pasted text safely before validation or import. Regex Capture GroupsUse numbered groups, named groups and non-capturing groups without making extraction code fragile. JSON Merge PatchUnderstand partial JSON updates, null semantics and safer API PATCH request review. JSON Array FilteringInspect JSON arrays, missing fields, duplicates and filter assumptions before transforming data. CSV CleanupClean CSV headers, delimiters, quotes, blank rows and encoding issues before conversion to JSON. XML Namespace DebuggingDebug XML namespace prefixes, default namespaces and XPath surprises in integration payloads. YAML Docker ComposeReview Docker Compose YAML indentation, environment variables, ports, volumes and service blocks. SQL GROUP BY DebuggingDebug grouped SQL reports, aggregates, HAVING filters and missing dimensions. SQL Date Range DebuggingReview SQL date ranges, inclusive boundaries, timezones and index-friendly filters. PostgreSQL EXPLAIN ANALYZERead PostgreSQL query plans, row estimates, loops, timing and index usage safely. MySQL Processlist DebuggingUse MySQL processlist evidence to inspect active queries, locks, sleep sessions and incidents. Redis SLOWLOG DebuggingUse Redis SLOWLOG to inspect expensive commands, latency symptoms and cache misuse. Docker Volume DebuggingDebug Docker volumes, bind mounts, permissions, persistence and missing files. Kubernetes CrashLoopBackOffInvestigate CrashLoopBackOff with logs, events, probes, env vars and container exit codes. Linux systemctl DebuggingUse systemctl status, restart history, unit files and journal evidence during service incidents. Git Branch CleanupClean local and remote Git branches safely after merges, releases and abandoned experiments. PHP Composer Dependency ConflictDebug Composer version conflicts, platform requirements, lock files and package constraints. Java Maven Dependency DebuggingDebug Maven dependency trees, version conflicts, exclusions and build-classpath surprises. Email Regex PythonValidate email-shaped strings in Python while keeping deliverability and account rules outside regex. Email Regex PHPUse PHP email validation, regex checks and filter_var without turning format checks into business truth. Regex Word BoundaryUse word boundaries for tokens, IDs and search terms without surprising Unicode or punctuation behavior. Regex Multiline AnchorsUnderstand anchors, multiline flags and line-by-line matching before parsing copied logs. Regex URL ExtractionExtract URLs from logs, Markdown and pasted text while knowing when a real URL parser is safer. curl Headers DebuggingInspect request and response headers with curl before changing API clients, proxies or CORS settings. curl Bearer TokenTest bearer-token APIs with curl while redacting secrets and separating auth from payload errors. Postman to curl DebuggingTurn a Postman request into a repeatable curl command for tickets, terminals and CI evidence. API Request Body ValidationDebug JSON request-body validation, content types, required fields and schema mismatch errors. API Correlation ID LoggingUse correlation IDs to connect frontend errors, gateway logs, service logs and database evidence. JWT Signature VerificationVerify JWT algorithms, keys and signatures without exposing real tokens or trusting decoded claims blindly. JSON Path QueryUse JSON path thinking to inspect nested payloads, arrays and optional fields before transforming data. JSON null vs undefinedSeparate JSON null, missing fields and JavaScript undefined before debugging PATCH and schema behavior. XML XPath DebuggingDebug XPath selectors, namespaces, attributes and text nodes in XML integrations. YAML Anchors and AliasesUse YAML anchors, aliases and merge keys carefully in CI, Docker and infrastructure configuration. CSV UTF-8 EncodingDebug CSV encoding, delimiters, byte order marks and broken characters before imports. PostgreSQL Connection LimitInspect active PostgreSQL sessions, pool pressure and connection limits before restarting services. MySQL Deadlock DebuggingRead InnoDB deadlock evidence and transaction patterns before changing indexes or retry logic. Redis Key NamingDesign Redis key names that are searchable, safe to expire and easier to debug during incidents. Linux Disk Space DebuggingFind which filesystem, directory, container or log stream is consuming Linux disk space. Nginx Access Log AnalysisUse access logs to inspect status codes, latency, upstream behavior and suspicious traffic. Python pip RequirementsDebug requirements.txt, pip installs, package versions and virtual environment mismatches. PHP ini ConfigurationFind which php.ini file is active for CLI, FPM and web requests before changing settings. Java Classpath DebuggingDebug classpath, missing classes, duplicate jars and service runtime differences in Java apps. Node.js package.json ScriptsRead npm scripts, environment variables and build commands before debugging Node.js deployments.

Site trust

Policies, maintenance and editorial references