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class parse_error : public exception;

This exception is thrown by the library when a parse error occurs. Parse errors can occur during the deserialization of JSON text, BSON, CBOR, MessagePack, UBJSON, as well as when using JSON Patch.

Member byte holds the byte index of the last read character in the input file (see note below).

Exceptions have ids 1xx (see list of parse errors).

uml diagram

Member functions

  • what - returns explanatory string

Member variables

  • id - the id of the exception
  • byte - byte index of the parse error


For an input with n bytes, 1 is the index of the first character and n+1 is the index of the terminating null byte or the end of file. This also holds true when reading a byte vector for binary formats.



The following code shows how a parse_error exception can be caught.

#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
        // parsing input with a syntax error
    catch (json::parse_error& e)
        // output exception information
        std::cout << "message: " << e.what() << '\n'
                  << "exception id: " << << '\n'
                  << "byte position of error: " << e.byte << std::endl;


message: [json.exception.parse_error.101] parse error at line 1, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
exception id: 101
byte position of error: 8

See also

Version history

  • Since version 3.0.0.

Last update: March 8, 2023