{}JSONLint
W001Warning

Leading byte-order mark (BOM)

The input begins with a UTF-8 BOM (allowed in JSONC).

What it means

In JSONC mode a leading byte-order mark (U+FEFF) is tolerated rather than rejected, but it is still non-standard and can trip up other parsers downstream.

Example

Invalid
\uFEFF{ "a": 1 }
Valid
{ "a": 1 }

How to fix it

Save the file as UTF-8 without BOM to be safe across all tools.

Validate your JSON to see this and every other issue highlighted in one pass.

Diagnostics on this page come from @jsonlint/core, the open-source engine that powers the JSONLint validator. Install it with npm install @jsonlint/core.