Code Explainer
Commercial use OK
380+ models
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Model:
+ GPT-5, Claude, Gemini
Paste code and get a plain-English walkthrough at the right audience level — junior dev, senior dev, non-technical stakeholder, or learn-the-language. Three-section output: what it does, step-by-step, why it works the way it does.
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Understand any code with AI explanations.
How to Use Code Explainer
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Use this tool via API
Automate this tool from your own code. OpenAI-compatible REST endpoint, Bearer-token auth, no extra SDK required. Token costs match the web interface.
curl -X POST https://api.free.ai/v1/chat/ \
-H "Authorization: Bearer sk-free-..." \
-H "Content-Type: application/json" \
-d '{"model": "qwen-coder", "messages": [{"role": "user", "content": "Write a Python function that reverses a string."}]}'Code Explainer — FAQ
Paste any code (or upload a file up to 500KB) and get a clear, line-by-line explanation in your choice of 4 audience levels: Junior dev (assumes basic syntax knowledge), Senior dev (assumes language fluency, focuses on architecture/design), Non-technical (no code experience — explains in business terms), or Learn-the-language (explains while teaching the language idioms).
ChatGPT / Cursor / Copilot Chat all explain code well — the difference is Free.ai is browser-based (no install, no $10-20/mo subscription) and the audience-level picker forces consistent register. Cursor ($20/mo) and Copilot ($10/mo) are inside-IDE; use them when in flow. Use Free.ai for ad-hoc explanations you want to share with a teammate, paste into a PR description, or use as a teaching aid.
Junior dev for onboarding (assumes they know loops/functions but not advanced patterns). Senior dev for code review prep (skips basics, dwells on architecture, design choices, gotchas). Non-technical for product/PM stakeholders (zero code, business outcomes). Learn-the-language for cross-language learning ("I know Python, explain this Rust" — call out the language-specific patterns).
When obvious bugs are present (off-by-ones, undefined behavior, security issues) the explainer will note them in a "Concerns" section. For systematic bug hunting use /code/debug/ (purpose-built bug finder) or /code/review/ (severity-graded audit). Explain mode focuses on understanding, not auditing.
Scales with code length and audience. Senior-dev explanations of a 50-line function: ~200 words + key annotations. Non-technical explanations: 100-150 words abstracting away mechanics. Learn-the-language: longest because it pauses to teach idioms — expect 300+ words for the same input.
Partially — paste the stack trace alongside the source. Better tool: /code/debug/ which is purpose-built for "code + error → root cause + fix" and produces a four-section structured response.
Qwen 3 Coder (free, default) handles ~95% of explanations well. DeepSeek R1 for code that requires deep reasoning to explain (cryptography, lock-free concurrency, complex business logic). Premium Claude Sonnet 4 / GPT-5 for cross-language idiom comparisons or when teaching unfamiliar languages — they have a richer model of language design tradeoffs.
Yes — JSON / YAML / TOML / Dockerfile / Kubernetes YAML / SQL / regex / shell scripts all work. The model auto-detects format and picks the right explanation framing. For dedicated SQL explanation use /code/sql/, for regex use /code/regex/.
Three sections: **What it does** (one-paragraph summary at the chosen audience level), **Step by step** (numbered walkthrough, each step ties to a code segment), **Why it works the way it does** (design choices, trade-offs, alternatives). Junior level adds vocabulary callouts; learn-the-language adds idiom comparisons.
Up to 12,000 characters (~180 lines) on the self-hosted path. Premium long-context models handle 200K+ characters — switch when explaining a whole module.
Code is sent to the model, processed, and discarded. Not stored, not used for training. Pick Qwen 3 Coder for maximum privacy — self-hosted on Free.ai's GPUs, source never leaves our infrastructure.
Yes — POST to /v1/chat/ with the explain system prompt (audience level) and the code as the user message. See /api/ for snippets.
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