OpenAPI / Swagger Viewer — Free Online Tool OpenAPI is a machine-readable HTTP API contract describing servers, operations, parameters, request bodies, responses, and security requirements. This…
Use this free online OpenAPI / Swagger Viewer directly in your browser. No signup required, no data leaves your device. Part of Utilier — a collection of 133+ developer utilities.
What is OpenAPI / Swagger Viewer? OpenAPI is a machine-readable HTTP API contract describing servers, operations, parameters, request bodies, responses, and security requirements. This offline viewer parses a JSON or YAML specification and renders a real endpoint table and schema browser, so a large contract is easy to scan without uploading it anywhere.
An OpenAPI document is both documentation and a contract: clients, tests, and gateways can use its path, parameter, and schema information to agree on the same interface. The endpoint list is most useful as an inventory; always inspect operation-level security, required parameters, request-body media types, and response codes before relying on a generated request.
Why use OpenAPI viewer? It turns a dense specification file into a scannable list of methods, paths, summaries, and data shapes before any client code is written.
When to use OpenAPI viewer Use it for onboarding to an unfamiliar API, reviewing a specification during code review, or checking which fields a schema expects before wiring up a request.
How to use OpenAPI viewer Paste an OpenAPI JSON or YAML document to browse its endpoints and schemas.
Paste the specification: JSON and YAML are both auto-detected — include a paths object and, ideally, a servers entry.Scan the endpoint table: Every method/path/summary combination from the spec is listed in one table.Expand a schema: Click a schema name to see its full JSON shape.Key features Real endpoint table: Lists every method, path, and summary — not just raw text.Schema browser: Expand any component schema to see its full shape.JSON and YAML: Auto-detects and parses either format.Local only: Nothing is uploaded — parsing happens entirely in your browser.Common use cases API onboarding: Map an unfamiliar API's surface in seconds.Spec review: Check route and schema changes before a release.Client planning: See what a schema expects before writing a request body.Examples Endpoint table GET /usersA row showing method GET, path /users, and its summary.Schema shape components.schemas.UserAn expandable entry showing id, name, and email fields.Common mistakes to avoid Assuming the sample server URL is correct Why it happens: Specs can list multiple environments.
How to avoid it: Check the servers array for the intended base URL.
Ignoring required schema fields Why it happens: The viewer shows the full shape, but required-ness needs a closer read.
How to avoid it: Expand a schema and check its "required" array before building a request.
Frequently asked questions Does this support YAML? Yes — paste either JSON or YAML and it's auto-detected.
Does this support XML or let me design my own endpoints? Not in this lightweight version — the fuller OpenAPI Viewer in the Mock API app supports XML import/export and lets you design and export your own endpoints as OpenAPI.
Privacy and availability Runs entirely in your browser — zero server processing No signup or account required Works offline once loaded Fast, lightweight, no external dependencies Available as a browser extension for Chrome and Firefox Tags JSON YAML HTTP Networking API Related tools OpenAPI to cURL Inspector — Convert OpenAPI/Swagger JSON operations into ready-to-run cURL request starters — a lightweight inspector, not a full spec browser.API Tester — Lightweight REST, GraphQL & WebSocket client with auth, body types, query params, and request history.JSON Beautifier & Validator — Format, minify and validate JSON. Reports the exact error location.JSON ↔ YAML — Convert JSON to YAML and YAML back to JSON.cURL Converter — Convert a curl command to fetch, Axios, React, Python, Go, PHP, Java or Rust — and fetch back to curl.All developer tools JSON Beautifier & Validator — Format, minify and validate JSON. Reports the exact error location.HTML Beautifier & Minifier — Indent or minify HTML. Content of pre/script/style is preserved.CSS Beautifier & Minifier — Pretty-print or minify CSS. Handles comments, strings, and nested at-rules.JavaScript Beautifier & Minifier — Format, minify, or obfuscate JavaScript. String, template, regex and comment aware.SQL Formatter — Format SQL queries: clauses on new lines, keywords uppercased.SQL Converter — Convert SQL INSERT statements or SELECT results to CSV, JSON, XML, YAML, or HTML.Markdown Preview — Live GitHub-flavoured-ish Markdown rendering (safe, HTML-escaped).Diff Checker — Compare two texts line by line with additions and deletions highlighted.Base64 / Base32 / Base58 / Base85 Encoder — Encode and decode text using Base64, Base32, Base58, Base85, or ASCII85.URL Encode / Decode — Percent-encode or decode text and query components, in any character set.HTML Entity Encode / Decode — Escape/unescape HTML special characters and numeric entities.ROT13 / ROT-N Encoder — Apply the ROT13 letter cipher (or any ROT-N shift) to text. ROT13 is its own inverse.JWT Decoder — Decode a JWT's header and payload. Optionally verify an HMAC signature.JWT Generator — Create a signed JWT (HS256/384/512) from a JSON payload and secret.Hash Generator — Compute MD5, SHA-1, SHA-256, SHA-384, SHA-512, and CRC-16 digests of text.HMAC Generator — Compute a keyed HMAC signature of a message (SHA-1/256/384/512).CRC32 Generator — Compute the CRC-32 (IEEE 802.3) checksum of text, shown as hex and decimal.Hash Verification — Compute a hash of your text (MD5, SHA-1/256/384/512 or CRC-32) and compare it against an expected value to confirm a match.Checksum Calculator — Upload a file to compute its SHA-1, SHA-256, SHA-384, SHA-512 and CRC-32 checksums for integrity verification.Text Compression — Compress and decompress text using GZip, Deflate, or Deflate-Raw algorithms.BCrypt Generator — Hash a password with bcrypt (Blowfish-based, salted) at a configurable cost, or verify a password against an existing bcrypt hash.AES Encrypt / Decrypt — Encrypt or decrypt text with AES-256-GCM using a password (PBKDF2-SHA256 key derivation). Output is base64 packing salt + IV + ciphertext.RSA Encrypt / Decrypt — Generate an RSA keypair and encrypt/decrypt short messages with RSA-OAEP (SHA-256). Keys are PEM. Best for small payloads (≈190 bytes at 2048-bit).UUID Generator — Generate cryptographically-random version 4 UUIDs in bulk.Password Generator — Generate strong random passwords with configurable character sets.Regex Tester — Test JavaScript regular expressions with live match highlighting and groups.Unix Timestamp Converter — Convert between Unix timestamps and human-readable dates (local & UTC).Timezone Converter — Convert a date and time between any two IANA time zones (DST-aware).Date Difference Calculator — Calculate the elapsed time between two dates as a calendar breakdown and in total units.QR Code Generator — Turn text/URLs into a QR code, optionally with a centered logo. Download as PNG.Color Picker & Converter — Convert between HEX, RGB(A), HSL(A), HSV, and CMYK. Pick a color visually.cURL Converter — Convert a curl command to fetch, Axios, React, Python, Go, PHP, Java or Rust — and fetch back to curl.JSON ↔ YAML — Convert JSON to YAML and YAML back to JSON.TOML Converter — Convert TOML to JSON or YAML and JSON/YAML back to TOML, with validation.JSON ↔ CSV / SQL — Convert JSON array to CSV, TSV, or SQL INSERT statements. Parse CSV/TSV back to JSON.Lorem Ipsum Generator — Generate placeholder text by paragraphs, sentences or words.Case Converter — Convert text between camelCase, snake_case, kebab-case, Title Case and more.Number Base Converter — Convert integers between binary, octal, decimal, hexadecimal, and custom bases (radix 2-36).Text / Binary / Hex / Decimal / Octal Converter — Convert between text, binary, hexadecimal, decimal, and octal. Auto-detects the input format.Slug Generator — Convert titles into clean, URL-friendly slugs. Strips accents and punctuation.CSS Unit Converter — Convert between px, rem, em, %, pt, pc, in, cm, mm, vw and vh.Image Converter — Turn an image into a Base64 data URI, CSS background, <img> tag or an SVG wrapper.Unicode Encoder / Decoder — Convert text to and from \uXXXX escapes, or list its Unicode code points.UTF-8 Encoder / Decoder — Convert text to its UTF-8 bytes (hex, decimal or binary) and decode bytes back to text.ASCII Converter — Convert text to and from character codes in decimal, hexadecimal or binary.Escape / Unescape — Escape and unescape strings for JSON, XML, JavaScript, CSV, and SQL contexts.Word & Character Counter — Live count of words, characters, lines, sentences, paragraphs and reading time.Text Formatter & Cleaner — Clean up text: remove blank lines, trim spaces, strip line numbers, sort/shuffle/reverse lines or words, remove punctuation, flip upside down.Advanced String Tools — Advanced string manipulation: remove accents, extract delimited text, filter lines, calculate similarity, character diff.Emoji Picker — Browse and click an emoji to copy it to your clipboard.Nano ID Generator — Generate compact, URL-safe unique IDs with a configurable size and alphabet.ULID Generator — Generate ULIDs — 128-bit, lexicographically sortable IDs (48-bit time + 80-bit randomness) in Crockford Base32, with an optional monotonic mode.UUID Validator — Check whether a string is a valid UUID and detect its version and variant.Random Number Generator — Generate cryptographically-random integers, decimals, primes, or fractions within a range.Random String Generator — Generate random strings from selectable character sets, or special formats (hex, binary, MAC address).Random Regex Generator — Generate random strings that match a regular expression pattern. Perfect for test data generation.ASCII Art Generator — Turn text into a figlet-style banner or convert an image into ASCII art. Copy, download as text or image, and share.Snowflake ID Generator — Generate and decode Twitter/Discord-style Snowflake IDs with a configurable epoch and bit layout.CSS Gradient Generator — Design linear or radial gradients with live preview and copy the CSS.Box Shadow Generator — Visually build a CSS box-shadow and copy the rule.CSS Grid & Flexbox Generator — Generate CSS Grid templates or Flexbox layouts with a live preview, then copy or download the CSS.Query Parameter Parser — Break a URL or query string into its individual parameters.Query String Builder — Assemble a URL-encoded query string from key/value pairs.robots.txt Generator — Generate a robots.txt with allow/disallow rules, crawl-delay and sitemap.sitemap.xml Generator — Turn a list of URLs into a valid XML sitemap..gitignore Generator — Combine common .gitignore presets for languages, OSes and editors.Dockerfile Generator — Scaffold a Dockerfile for many stacks with multi-stage builds, env vars, ports, a non-root user and healthcheck..htaccess Generator — Generate common Apache .htaccess rules (HTTPS, www, caching, compression).Server Config Generator — Generate nginx, Apache or Tomcat configs for HTTPS, reverse proxy, load balancing, API gateway, caching and rate limiting.XML Beautifier / Minifier — Pretty-print, minify, validate XML. Convert to JSON or CSV.Cron Expression Parser — Translate a cron expression into a plain-English schedule.Cron Expression Generator — Build a cron expression from simple schedule fields with a live description.Regex Generator — Pick a common validation pattern and test it against sample text.CIDR Calculator — Expand an IPv4 CIDR block into network, broadcast, host range and mask.Subnet Calculator — Enter an IP and a subnet mask (dotted or prefix) to compute the subnet details.IP Address Converter — Convert IPv4 addresses to and from decimal, hexadecimal, octal, and binary formats.Punycode Converter — Convert internationalized domain names (IDN) to and from Punycode (xn--) ASCII form.CSP Generator & Evaluator — Build a Content-Security-Policy from directives and lint any pasted CSP for common weaknesses.Kubernetes Manifest Generator — Generate a Kubernetes Deployment + Service manifest (image, replicas, ports, env vars) as YAML.Docker Compose Generator — Build a docker-compose.yml with a primary service plus optional Postgres, MySQL, Redis or Mongo add-ons.Terraform (AWS) Generator — Generate Terraform HCL for common AWS resources: EC2 instance, S3 bucket or security group.GitHub Actions Generator — Generate a CI workflow (.github/workflows/ci.yml) for Node, Python, Go, Java or Rust with push/PR triggers.AWS IAM Policy Generator — Generate AWS IAM policy JSON documents with common actions for S3, EC2, Lambda, DynamoDB, and more.GitLab CI Generator — Generate .gitlab-ci.yml pipeline configurations for Node.js, Python, Docker, Terraform, and Go projects.Nginx Config Generator — Generate production-ready Nginx server blocks for reverse proxy, SPA, or static sites with SSL, gzip, and security headers.SSL/TLS Certificate Decoder — Decode PEM-encoded X.509 certificates — view subject, issuer, validity, SAN, and expiration status.Helm Chart Generator — Generate Kubernetes Helm chart scaffolding (Chart.yaml, values.yaml, deployment template) with configurable options.Dockerfile Linter — Lint Dockerfiles offline — checks for best practices like pinned tags, apt cleanup, COPY vs ADD, exec-form CMD, and more.Terraform Backend Config — Generate Terraform backend configuration for S3, GCS, Azure, Consul, or local state storage with provider setup.Kubernetes Policy Checker — Analyze Kubernetes YAML offline for risky security settings, mutable images, missing resources, and production-readiness gaps.Terraform Static Analyzer — Scan Terraform HCL offline for risky AWS patterns such as public admin ingress, unencrypted storage, missing provider pins, and static credentials.IAM Policy Risk Analyzer — Review AWS IAM policy JSON offline for wildcard permissions, broad resources, escalation-sensitive actions, and risky trust patterns.Architecture Diagram Generator — Create Mermaid architecture diagrams offline from service and dependency lists for system design, DevOps handoffs, and runbooks.Incident Runbook Builder — Generate practical incident response runbooks offline with triage, diagnosis, rollback, communication, validation, and follow-up sections.SLO Error Budget Calculator — Calculate availability, allowed downtime, error budget consumption, remaining budget, and burn rate for SRE and operations planning.Image Resizer & Compressor — Crop, resize an image to exact pixel dimensions and re-encode it at a chosen quality to shrink the file size.Image Cropper — Crop an image with a draggable, resizable selection box. Move it, drag any of the 8 handles, and lock to a fixed aspect ratio or crop freely.SVG Viewer — Paste SVG markup to preview it live and export it as a data URI or PNG.Barcode Generator — Generate a Code 128 barcode from text and export it as PNG.Favicon Generator — Create favicon PNGs from a letter or emoji with custom colors, in every common size.Fake Data Generator — Generate mock people or products (JSON/XML/CSV) or placeholder images (PNG/JPG/WEBP/GIF) for prototyping.SQLite Viewer — Open a .sqlite/.db file in the browser, browse tables and run SQL — fully client-side.Clipboard History — The last 10 things you copied from any tool. Click to copy again.HTTP Status Codes — Searchable reference of HTTP response status codes with their names and meanings.Keyboard Event Tester — Inspect key events (key, code, keyCode, modifiers) and browse the ASCII chart with code↔character conversion.Developer Calculator — Evaluate math expressions with functions (sqrt, sin, cos, log), constants (pi, e), operators (^, %, /), and bitwise operations (and, or, xor, not, shl, shr).OpenAPI / Swagger Viewer — Browse an OpenAPI/Swagger document's endpoints and schemas in a readable list — paste JSON or YAML, entirely offline.OpenAPI to cURL Inspector — Convert OpenAPI/Swagger JSON operations into ready-to-run cURL request starters — a lightweight inspector, not a full spec browser.JSON & HAR Secret Redactor — Redact likely secrets, authorization headers, and email addresses locally before sharing data.SVG Optimizer & Inspector — Minify SVG markup locally and flag common preview and accessibility gaps.Web Manifest Validator — Validate a PWA web manifest locally and inspect essential install metadata.CSS Specificity Calculator — Compare CSS selectors locally and see the cascade specificity tuple.Cookie Parser & Set-Cookie Builder — Parse Cookie and Set-Cookie values, then build a standards-friendly response header locally.Unicode Security Inspector — Find invisible Unicode, bidi controls, mixed scripts, and common confusable characters locally.Regex Extractor — Extract every regex match and capture group with locations, then export JSON or CSV locally.Cron Expression Explainer — Explain five-field cron schedules and preview the next 10 runs in a selected timezone.CSS clamp() Fluid Scale Generator — Generate a responsive CSS clamp() value from minimum and maximum viewport and size targets.Unit Converter — Convert between units of length, weight, temperature, area, volume, speed, time, data size, and pressure.JSONPath Query — Query JSON data using JSONPath expressions ($, dot notation, arrays, wildcards, recursive descent).HTML ↔ Markdown Converter — Convert HTML to Markdown and Markdown to HTML. Handles headings, lists, tables, links, images, and code blocks.HAR File Analyzer — Inspect a browser HAR capture locally: slow requests, failures, domains, and transfer size..env Parser & Converter — Validate environment variables locally and convert .env entries to JSON or Docker Compose YAML.JSON Schema Validator — Validate JSON locally against a practical JSON Schema subset and see precise field-level errors.HTTP Header Analyzer — Parse HTTP headers locally and identify caching, CORS, cookie, and security-header concerns.Cheat Sheets — Instant-search reference cards for git, docker, kubectl, terraform, vim, bash, and regex. Click any command to copy.Kubernetes YAML Generator — GUI wizard to generate production-ready Kubernetes manifests: Deployment, Service, Ingress, ConfigMap, Secret, PVC, HPA.Markdown Writer — Write markdown with a quick-action toolbar. Preview as rendered HTML, copy or download in multiple formats.API Tester — Lightweight REST, GraphQL & WebSocket client with auth, body types, query params, and request history.JSON to TypeScript — Convert JSON objects to TypeScript interfaces. Handles nested objects, arrays, and optional/null fields.CSS Animation Generator — Create CSS animations with live preview. Adjust timing, pick presets, upload an image to test. Copy the generated CSS.Image ↔ Base64 — Convert images to Base64 data URIs, or paste a data URI to preview and download the image. Max 2MB.HTML Table Generator — Visual table builder — set rows and columns, fill in data, generate clean HTML table code.Credit Card Validator — Validate card numbers using the Luhn algorithm. Identifies card type (Visa, Mastercard, Amex, Discover, etc.).