JSON Streaming & Partial Parser

Parse incomplete or streaming JSON — automatically completes truncated output from LLM APIs, streaming HTTP responses, and partial data chunks. See what was parsed and what was added to make it valid.

Partial / Incomplete JSON
Parsed Output

⚡ What gets fixed

  • Unclosed objects {"a": 1
  • Unclosed arrays [1, 2, 3
  • Truncated strings "hello wor
  • Missing commas between values
  • Trailing commas [1, 2,]
  • Partial key-value pairs {"key":
  • Multiple levels of unclosed nesting

🤖 LLM Use Cases

  • OpenAI / Claude streaming API responses
  • JSON output cut off by token limits
  • Structured output that didn't close cleanly
  • Real-time UI from streaming chunks
  • Debug incomplete LLM-generated JSON
  • Extract partial data before full response

🔧 How it works

  • Attempts native JSON.parse() first
  • Tracks open bracket/brace stack
  • Closes unclosed strings at truncation point
  • Adds missing closing brackets in order
  • Handles dangling keys with null values
  • Reports exactly what was added

JSON Streaming Parser Guide

Real JSON is either valid or it isn't — JSON.parse() gives you an all-or-nothing result with no way to salvage a response that got cut off mid-stream. That's a constant problem with LLM APIs: a token limit, a dropped connection, or a UI that wants to render output as it arrives can all leave you holding a truncated fragment like {"items": [{"name": "wid that native parsers simply reject.

This tool tries a normal parse first, and only on failure walks the bracket/brace stack to figure out what's still open — closing dangling strings at the truncation point, appending the missing closers in the correct order, and filling incomplete key-value pairs with null — then reports exactly what it added so you know the repair isn't silently hiding a real bug.

Frequently Asked Questions

How is this different from JSON Repair?

JSON Repair fixes malformed-but-complete JSON (wrong quotes, trailing commas, comments). This tool specifically targets JSON that was cut off mid-stream — the document is structurally incomplete, not just syntactically wrong, so the fix strategy (closing open brackets) is different from repairing a finished-but-broken document.

Is the recovered data trustworthy?

Everything up to the truncation point is your original data, untouched. Anything the parser had to invent (a closing bracket, a null for a dangling key) is listed in the output summary so you can decide whether the partial result is usable or you need to wait for/re-request the full response.

Can I use this to debug streaming API integrations?

Yes — paste a raw chunk captured mid-stream from an OpenAI, Anthropic, or other structured-output API to see the JSON shape as it exists at that point, which is useful for building incremental UI rendering or diagnosing why a stream handler is failing.