JsonMind Guides
Practical developer guides
Short, evidence-based guides for the errors and decisions developers hit every week. Every guide links to a browser tool, cites the relevant specification, and states its limits.
JSON & Data
5YAML Indentation Error: Fix Mapping Values, Tabs and Kubernetes YAML
Fix YAML indentation errors: mapping values are not allowed here, tabs vs spaces, block scalars, list indentation, anchors and Kubernetes manifests.
CSV to JSON: Handle Quotes, Commas, Encoding and Nested Data
Convert CSV to JSON without breaking on quoted commas, line breaks, BOMs or mixed types. Includes a repeatable validation workflow.
Unexpected token < in JSON at position 0: How to Fix It
Learn why JSON.parse fails with unexpected token, unexpected end of input, or invalid JSON errors, and how to find the real payload before changing code.
Generate TypeScript Types from JSON: A Practical Guide
Turn real JSON samples into accurate TypeScript interfaces, handle nullable and optional fields, and avoid the common mistakes that make generated types unsafe.
JSON vs YAML: Differences, Pitfalls and When to Use Each
Compare JSON and YAML syntax, comments, anchors, data types and tooling. Learn when each format fits APIs, configuration, CI and Kubernetes.
Encoding & Text
5Cron Expression Syntax: A Practical Guide with Examples
Read and write cron schedules for minutes, hours, days and weekdays, avoid the classic day-field trap, and verify expressions before deploying them.
Regex Cheat Sheet: Common Patterns and How to Test Them
A practical regular expression reference for anchors, classes, quantifiers, groups and lookarounds, with patterns, flags and safety checks that prevent surprises.
Base64 and Unicode in JavaScript: Fix btoa Errors and Mojibake
Learn why btoa fails on Chinese, Japanese, and emoji text, how to encode UTF-8 bytes correctly, and how to decode Base64 without garbled output.
Unix Timestamp: Seconds vs Milliseconds and How to Convert Them
Avoid 1970 dates and year-57770 bugs by keeping Unix timestamp units straight. Includes JavaScript, SQL, JWT, and cron conversion examples.
UUID vs ULID: Which Identifier Should Your Application Use?
Compare UUID v4, UUID v7, and ULID for sortability, database indexes, URL safety, and distributed systems, with a clear recommendation for new projects.
Security & Authentication
3JWT exp, iat and nbf Explained: How to Debug Expired Tokens
Understand JWT expiration claims, clock skew, and signature errors. Learn how to decode a token safely and fix expired or not-yet-valid token failures.
JWT vs Session Cookies: Which Authentication Should You Use?
Compare stateless JWTs and server-side sessions for revocation, scaling, XSS, CSRF and mobile clients, with a practical decision guide.
Password Hashing: Why SHA-256 Fails and How bcrypt Works
Understand why fast hashes fail for passwords, how bcrypt and Argon2id work, and which settings and operational controls actually protect stored credentials.
API & Contracts
6HTTP 429 Too Many Requests: Retry-After, Backoff, and Retry Storms
Understand what 429 Too Many Requests means, parse Retry-After seconds and HTTP-dates, design jittered exponential backoff with a cap, and avoid retry storms.
Idempotency Keys for APIs: Safe Retries for Payments and State Changes
Design idempotent APIs that survive retries: key generation, header placement, storage schema, request fingerprints, replay, TTL, and payment failure semantics.
JSON Schema Validation: Common Errors and How to Fix Them
Diagnose JSON Schema validation failures, understand required, type, additionalProperties and format errors, and validate payloads before they reach production.
Convert cURL to fetch or Axios Without Breaking the Request
Map cURL flags to fetch and Axios options, avoid quoting and content-type mistakes, and verify the converted request against the original.
Fix CORS Preflight Errors: Missing Access-Control-Allow-Origin
Diagnose CORS preflight failures with the browser, curl, and server logs. Learn which headers are required and why credentials break wildcard origins.
HTTP Status Codes for APIs: 4xx vs 5xx and What to Fix First
A practical debugging guide to HTTP status codes, including 400 vs 422, 401 vs 403, 404 vs 410, 429 retries, and 502 vs 504 gateway failures.
Images & Media
3EXIF Metadata Privacy: What Photos Reveal and How to Remove It
What EXIF, XMP, and IPTC metadata reveal about location, device, and time, which edits and platforms strip it, and how to verify removal.
How to Compress Images for the Web Without Losing Quality
Reduce image file size with resizing, format choice, quality settings and modern formats, and verify the result at the size users actually see.
WebP vs AVIF vs PNG: Which Image Format Should You Ship?
Compare WebP, AVIF, PNG, and JPEG for photos, screenshots, transparency, and animation, with a practical fallback strategy and conversion workflow.
Documents & Conversion
3Accessible PDFs: Tagged Structure, Reading Order, and Verification
How tagged PDF structure, reading order, alt text, headings, tables, language metadata, and OCR text layers work, what conversion destroys, and how to test before publishing.
Merge and Split PDFs Without Uploading Your Files
Combine, split, reorder and compress PDFs in the browser, and learn when page-level edits preserve layout and when they do not.
PDF to Word Conversion: What Survives and What Breaks
Understand why PDF-to-Word output changes layout, when OCR is required, and how to verify a converted document before sending it to a client.
Reviewed against primary specifications and linked sources.
JsonMind guides are written and reviewed by the engineering team. We check each guide against the relevant RFC or vendor documentation, link the primary sources, and update the guide when behavior changes.
Primary sources are linked at the end of each guide.