Guides are written by the Spoold Editorial Team and reviewed for practical accuracy against the related tools. Read our Editorial Policy for update and correction standards.
Short, practical guides for JSON, CSV, Docker Compose, regex, URLs, security checks, and SEO workflows inside Spoold.
50
10
Free curl diff checker online: paste two curl commands and see header, URL, auth, and body differences. Use Spoold curl Compare as your curl diff tool—client-side, no upload.
Showing 50 of 50 articles
Compare curl request online: paste two HTTP curls from DevTools or Postman and diff method, URL, headers, auth, and body. Free Spoold curl Compare—no upload.
Find the curl difference between two requests—Authorization, headers, query, and JSON body. Use Spoold curl Compare to spot token drift and payload changes online.
How to compare two Production or staging curl requests copied from Chrome DevTools or Postman. Use Spoold curl Compare to diff headers, auth, and body—or paste into curl Online to Send a single request.
Free image token calculator online: estimate GPT-4o, Claude, and Gemini vision tokens from width × height or an upload. Plan multimodal cost before you call the API—runs in your browser.
Free token calculator online: count GPT / LLM tokens with tiktoken (cl100k, o200k), estimate cost, and convert tokens to words (e.g. 10000 tokens ≈ 7,500 words). Client-side tiktoken online tool.
Free YAML diff / YAML compare online: paste two YAML files for a Monaco side-by-side or inline diff, unified output, and validity hints. Client-side—no upload.
Free unix timestamp converter online: paste epoch seconds or milliseconds to get UTC, local time, and ISO dates—or convert a date back to a timestamp. Instant, client-side.
Free UUID validator and formatter online: paste a UUID or GUID to check version, then reformat with hyphens, uppercase, or braces. Instant UUID checker—runs in your browser.
Free gzip decompress online: paste Base64 or hex gzip data (H4sI / 1f8b) to inflate text, or compress text to gzip. Gunzip / ungzip in your browser—no upload.
Free HTML renderer online: paste HTML with CSS and JavaScript for a sandboxed live preview. Same Spoold tool as HTML Preview—render HTML in your browser without a local server.
Clean JSON objects and API payloads by removing null values, empty strings, empty arrays, and empty objects. Learn safe cleanup rules, examples, and when not to strip fields.
Open, filter, dedupe, sort, and summarize large CSV or TSV files in the browser without Excel. Learn a practical workflow for big exports and safer manual execution.
Understand Docker Compose ports syntax, host-to-container mappings, localhost access, expose vs ports, and common port conflict errors in docker-compose.yml files.
Validate Docker Compose YAML before running it. Check syntax, services, images, ports, volumes, environment variables, depends_on, healthchecks, and deployment risks.
Create practical regex patterns for logs. Learn how to match timestamps, levels, request IDs, IP addresses, URLs, status codes, and error messages from text samples.
Use regex to extract identifiers, email addresses, IP addresses, URLs, UUIDs, order IDs, and request IDs from pasted text, logs, CSV snippets, and support tickets.
Understand Microsoft Safe Links, Proofpoint, Mimecast, and other wrapped URLs. Learn why links are rewritten, how to decode the destination, and how to inspect safely.
Inspect shortened links, tracking URLs, Safe Links, QR destinations, and redirect chains safely. Learn what to check before opening an unknown URL.
Understand Lighthouse performance, accessibility, best practices, SEO, Core Web Vitals, audits, opportunities, diagnostics, and what to fix first.
Use this Open Graph checklist to improve social previews, Slack and Discord shares, Twitter/X cards, title tags, descriptions, canonical URLs, and preview images.
Use Spoold's free CSV Operations tool to query CSV, TSV, and Excel .xlsx files online. Filter rows, select columns, find unique values and duplicates, dedupe CSV data, compare columns, count by category, sort rows, and run numeric summaries in your browser.
Generate Cloudflare R2 CORS JSON for public reads, browser uploads, signed downloads, and presigned URL workflows. Learn AllowedOrigins, AllowedMethods, AllowedHeaders, ExposeHeaders, MaxAgeSeconds, and Wrangler-ready config.
Cloudflare R2 presigned URLs still need bucket CORS when used from a browser. Learn how to allow PUT, POST, GET, Content-Type, x-amz-* headers, ETag exposure, localhost origins, and preflight requests.
Generate AWS S3 CORS policies for browser uploads, public reads, signed downloads, and presigned URLs. Learn CORSRules, AllowedOrigins, AllowedMethods, AllowedHeaders, ExposeHeaders, MaxAgeSeconds, and put-bucket-cors.
Troubleshoot Cloudflare R2 CORS errors in browser apps. Fix missing Access-Control-Allow-Origin, failed preflight OPTIONS, blocked Content-Type or x-amz-* headers, localhost origins, and hidden ETag response headers.
Create a CORS policy for browser uploads to object storage. Learn how origins, PUT/POST methods, Content-Type, x-amz-* headers, preflight OPTIONS, credentials, and ETag exposure work for S3 and Cloudflare R2.
Free online curl comparator and curl diff tool. Paste two curl commands, compare method, URL, headers, query params, auth, cookies, and body with Monaco diff and structured tables. Client-side, no upload — learn workflows, examples, and FAQs.
Free online JSON diff and JSON compare tool. Paste original and modified JSON, see added/removed/changed paths with semantic deep compare, Monaco DiffEditor, Report/Side/Unified views, export JSON/CSV/TXT, save/share links — ignores object key order, runs entirely client-side with no upload.
Free online OpenAPI viewer and Swagger viewer with a built-in curl generator. Paste OpenAPI 3.x or Swagger 2.0 JSON/YAML, browse operations by tag, pick a server, and copy a ready-to-run curl command per endpoint. Learn how base URLs, path parameters, query strings, request bodies, and security placeholders are built into each curl command — all client-side, no upload.
Learn what JSON Schema is, which drafts matter (4–2020-12), how SchemaStore helps, and how to use a free browser validator for APIs, configs, and package.json.
Learn what TOML is, how online formatting and validation help Rust and Python configs, why comments disappear on format, and how to use Spoold’s free browser tool.
Copy-paste sample QR payloads: URLs, plain text, Wi‑Fi (WIFI:), and vCard (BEGIN:VCARD). Free online QR generator; sample PNGs for Spoold, the QR tool, and hello text. WiFi QR, vCard QR, developer samples.
Create a scannable QR code for your website, Wi‑Fi guest network, or vCard contact in seconds. Free online QR code generator and scanner: website QR, WiFi QR, vCard QR, URL to QR, PNG/SVG download, test scan. No sign-up.
Copy the smallest valid PDF in hex or base64. Minimal valid pdf file bytes hex and base64 pdf for testing parsers, APIs, and viewers. Paste into our free PDF viewer to preview.
Discover how Magic Box instantly detects JSON, HTML, curl, JWT, CSV, regex, and 20+ formats. Learn how it adapts to your patterns and suggests workflows to accelerate your development.
Free online color picker with hex to RGB, RGB to hex, and HSL conversion. Pick colors with visual picker or eyedropper. WCAG contrast checker, shareable URL, palette export. No sign-up.
Create flowcharts and flow diagrams online by clicking to add nodes and dragging to connect. Auto-styling for database, API, user. Templates, export, share. No syntax—visual flowchart maker in the browser.
Learn what UUIDs are, when to use v4, v1, v7, or nil, and how to generate, validate, and export UUIDs with our free UUID Generator tool. Best practices and common pitfalls.
Format and beautify SQL online with our free SQL Formatter. Supports PostgreSQL, MySQL, SQLite, T-SQL, BigQuery, and 10+ dialects. Uppercase keywords, 2 or 4 space indent, copy, download, share. No install.
Edit Go, Rust, and Java online with Monaco syntax highlighting, format, and run (JS/Python). One editor for systems programming, microservices, and enterprise code. Free, no install.
Create flowcharts, sequence diagrams, class diagrams, ER diagrams, and Gantt charts with Mermaid syntax. Free online Mermaid editor with live preview, export to SVG/PNG, and GitHub-ready diagram-as-code. No design tools required.
Edit and run code in 40+ languages with Monaco (VS Code engine), syntax highlighting, format, and run JS/Python in the browser. Free, private, no install.
Write and run Python in the browser with our free online Python editor. Pyodide-powered execution, Monaco syntax highlighting, format on save, and share via link. No installation—ideal for learning, snippets, and quick algorithms.
Edit JavaScript and TypeScript in the browser with Monaco, syntax highlighting, and run support. No install—perfect for snippets, learning, and quick API or regex tests.
Master JSON formatting with our comprehensive guide. Learn best practices, common pitfalls, and how to use the JSON Formatter tool effectively.
Understand JWT structure, decode tokens safely, and inspect claims, expiry, and signatures. A complete guide with best practices and our free JWT Decoder tool.
Turn curl commands into JavaScript fetch or axios code in one click. Parse headers, body, and auth—with examples, fetch vs axios comparison, and best practices.
Test HTML, CSS, and JavaScript in the browser with no server. Live rendering, responsive preview, sandboxed iframe, and shareable links. Free online HTML preview tool for prototyping and debugging.
Convert CSV to JSON with auto-delimiter detection, table view, and export to JSON, SQL, or Markdown. Best practices, common pitfalls, and how to use the CSV Viewer tool.
Put these tutorials into practice with our free developer tools. No sign-up required.
Explore Tools