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Practical guides for developers working with JSON data, APIs, and data tools.
How to Fix Common JSON Parse Errors
The real Node.js and Python error for each common cause - trailing commas, single quotes, comments, NaN, unescaped backslashes, HTML error pages and invisible characters - and how to fix it.
Read Article →JSONPath Cheat Sheet: Syntax and Tested Examples
Every expression run against one sample document under RFC 9535: wildcards, slices, filters and functions, bracket notation for awkward keys, the jq and JSON Pointer equivalents, and where jsonpath-plus disagrees.
Read Article →Why JSON Loses Big Numbers (and How to Keep IDs and Decimals Exact)
Why JavaScript turns a 19-digit ID into a different number, why 12.50 comes back as 12.5, how Python, Java and Go compare, and four ways to keep IDs and decimals exact.
Read Article →How to Spot Breaking Changes in a JSON API Response
A type change, a rename and a newly nullable field, caught three ways: a structural comparison, a dependency-free Node.js check for CI, and JSON Diff in the browser.
Read Article →How to Run a cURL Command Online and Extract JSON Keys
Three real APIs run through the online cURL runner, keys extracted from each: a weather API that returns columns instead of rows, a JSON POST, and a paginated search where one response gives the wrong type - and a second one fixes it.
Read Article →Null, Missing, or Unknown: How Jackson, Pydantic and Zod Handle JSON That Doesn't Match Your Model
Thirteen mismatched payloads through four libraries. Jackson accepted almost all of them - truncating 42.7 to 42 and turning a missing ID into 0 - Jackson 3 flipped the unknown-field default, and only Zod keeps "missing" and "null" apart. With the configuration that makes each one strict.
Read Article →Why Your Browser Blocks API Calls: CORS Explained
What "blocked by CORS policy" actually means, why the request usually reached the server anyway, when a preflight fires, and the four ways to fix it - including what a proxy really costs you.
Read Article →Processing Large JSON Files Without Running Out of Memory
Measured memory and timing for jq, Python and NDJSON on a 120 MB document. Why plain jq is not streaming, what --stream costs, and how to inventory the key paths of a file far larger than RAM.
Read Article →Jackson vs Gson vs Moshi: Choosing a Java JSON Library
A technical comparison of the three main JVM JSON libraries: architecture, unknown-property defaults, deeply nested payloads, Spring Boot integration, and a JMH harness to benchmark them on your own data.
Read Article →JSON Tools for Developers: What to Use for Each Job
Which tool to reach for on each everyday JSON job - formatting, validating, exploring structure, diffing, API testing, and command-line work - including when not to use this site's own tool.
Read Article →Working with JSON in Python: A Complete Guide
Everything you need to know about JSON in Python: parsing with json.loads, reading and writing files, handling dates and custom types, using requests with APIs, and processing large files with streaming.
Read Article →JSON Schema: A Practical Guide to Validating JSON
Learn how to use JSON Schema to validate data structure - defining types, required fields, string patterns, number ranges, array constraints, nested objects, and conditional validation with if/then/else.
Read Article →JSON vs XML: A Detailed Comparison
JSON and XML compared on 50,000 real-shaped records: measured size before and after gzip (a 53% gap shrinks to 7%), parse time and memory in Python and Chromium, and when each format is the right choice.
Read Article →How to Extract All Keys from a JSON Object (JavaScript, Python, jq)
Six ways to extract every key path from a JSON object - no-code, JavaScript, Python, Ruby, and jq - each run on the same awkward document. The test found a bug in a common recursive function, a jq command that always returns nothing, and a key that fools every method but JSONPath.
Read Article →Common JSON Structures You'll Encounter in REST APIs
Master the most common JSON patterns in production APIs: envelope responses, pagination, error objects, nested resources, authentication tokens, rate limits, webhooks, and GraphQL.
Read Article →Understanding Nested JSON Objects and Arrays
A complete guide to navigating nested JSON - dot notation, bracket notation, safe access patterns in JavaScript and Python, iterating arrays, flattening structures, and JSONPath queries.
Read Article →What is JSON? A Complete Beginner's Guide
What JSON is, its six data types and syntax rules, and what happens at the edges: large IDs that JavaScript silently rounds, NaN that Python writes and JavaScript rejects, and duplicate keys - each tested in Node.js and Python.
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