
Codewars
Exercism
LeetCode
CodinGame
CodeCombat
HackerRank
Google's Python Class
CheckIO is a web site with a mission: To teach JavaScript and Python coding skills through a game-playing interface. It is designed to teach new skills or improve existing skills through completing challenges.

JSONLint
JSON-Formatter.app
Code Beautify JSON Validator
betterjson.com
CSVJSON
DomainProtect
ExtendsClass JSON Formatter
Browser-based JSON toolkit with verifiable browser-local workflows.
Which is more popular?
Based on our record, CheckIO seems to be more popular. It has been mentioned 46 times since March 2021.
Website, pricing, platforms and company facts side by side.
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| Website | checkio.org | safejson.dev |
| Pricing | — | |
| Company | — | Startup from the United States · 1 - 9 employees · 2026 |
| Listed in |
In their own words, as submitted to SaaSHub.


No description of CheckIO yet.
SafeJSON is a browser-based JSON toolkit for developers who work with API responses, webhook payloads, JWTs, JSONPath queries, and JSON Schema validation. It includes JSON formatting, validation, viewing, diffing, JWT decoding, JSONPath querying, and schema validation. Core JSON workflows are...
What each product offers, as listed by its team.


Possible disadvantages
An editorial look at what each product does well and who it suits.


Overall verdict
Why this product is good
Recommended for
Overall verdict
Why this product is good
Recommended for
Walkthroughs and reviews on video.
Intro Video. How to get maximum from CheckiO
No SafeJSON.dev videos yet. You could help us improve this page by suggesting one.
How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing CheckIO and SafeJSON.dev.
SafeJSON.dev's answer:
Safejson runs all JSON processing 100% locally in the user's browser, never uploading any sensitive JSON payloads to external servers. Most competing JSON tools send your confidential data to their backends for parsing, while we guarantee end-to-end client-side privacy alongside a full suite of JSON utilities like diff comparison and JWT decoding.
SafeJSON.dev's answer:
Frontend built with vanilla JavaScript + modern browser native APIs for local file handling and parsing, lightweight CSS framework for responsive UI, Lemon Squeezy for subscription & license management, pure client-side JSON parsing libraries with no server-side data persistence.
SafeJSON.dev's answer:
Users handling API keys, production secrets or private business data avoid data leakage risks with our local-only processing. We offer the same rich feature set as mainstream JSON tools, but with stronger privacy protection, flexible affordable subscription plans, and device-bound license activation without forced account registration.
SafeJSON.dev's answer:
Backend/frontend developers, DevOps engineers, cybersecurity professionals, and indie SaaS builders who regularly work with sensitive JSON data and prioritize data privacy, including enterprise developers dealing with confidential production payloads.
SafeJSON.dev's answer:
As a developer, I repeatedly faced anxiety when pasting sensitive API JSON into public online formatters, knowing the data could be logged or leaked on third-party servers. I built SafeJSON to fix this pain point: a fully client-side JSON toolkit that keeps all user data local, while packing all the everyday features developers need, and launched it as an indie MicroSaaS with fair pricing.
SafeJSON.dev's answer:
Individual freelance full-stack developers handling client confidential project data Small cybersecurity consultancies auditing API JSON payloads Indie SaaS engineering teams managing internal backend configurations DevOps specialists working with production environment JSON secrets
Share your experience with using CheckIO and SafeJSON.dev. For example, how are they different and which one is better?
External articles and on-site reviews we used to compare the two products.


CheckiO is a platform with coding games created for different levels of programmers, from beginners to advanced levels. Using fun and engaging methods, you can use coding games to solve challenges in TypeScript and...
CheckIO is available in English and Spanish. The platform was designed by a group of engineers and now has a number of customers all over the globe who may use it to improve their programming speed and abilities by...
Checkio is the most whimsical HackerRank alternative on this list. It’s also focused on two languages: Python and TypeScript. On this site you’ll be thrown into a gamer’s paradise that includes robot mollusks and...
We have no reviews of SafeJSON.dev yet. Be the first one to post
Recommendations tracked on public social media and blogs since March 2021.


Have you heard of CheckIO (https://checkio.org/)? They have a gameified "Mario world" of coding challenges that are smaller and come with more explanation, tests to guide you through edge cases and provide hints. The challenges start... Source: almost 3 years ago
Cyber isn't gonna be a light switch, where you can flip it and be good. Don't be too hard on yourself. Start with some hands on stuff like https://tryhackme.com or checkio.org. You could look at certs like Security+ or CySA+ for some... Source: about 3 years ago
Much better to get your hands dirty than watching the videos. Try: https://checkio.org/. Source: over 3 years ago
Tracking SafeJSON.dev since Jun 2026.
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Practice and level up your development skills and prepare for technical interviews.
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