When importing a JSON file containing numbers with 17 significant digits (the maximum meaningful precision for IEEE 754 double-precision floats), Vite 8 truncates them to 16 significant digits in the bundle output. This silently changes the runtime value.

Inline number literals in JS/TS files are not affected - only numbers from JSON imports.

Reproduction

https://github.com/elderapo/vite-float-precision-bug

git clone https://github.com/elderapo/vite-float-precision-bug
cd vite-float-precision-bug
npm install

# Vite 8 - 4/8 values are corrupted
npx vite build && npx vite preview

# Vite 7 - all 8 values preserved correctly
npm install vite@7
npx vite build --outDir dist-v7 && npx vite preview --outDir dist-v7

Example

src/data.json:

{ "values": [114.35143799257997, 406.31486713248995] }

src/main.js:

import data from "./data.json";
console.log(data.values[0] === 114.35143799257997); // false in Vite 8, true in Vite 7
console.log(data.values[1] === 406.31486713248995); // false in Vite 8, true in Vite 7

What happens in the bundle:

The last significant digit is dropped, which maps to a different IEEE 754 double.

Impact

Any application relying on exact float values from JSON will silently get wrong data. This affects physics simulations, deterministic algorithms, coordinate data, scientific datasets, etc.

Environment

• Vite 8.0.1
• Node.js v22
• Linux x86_64