How to Remove a Character from a String in C++

Short answer: by position use s.erase(index, 1). To remove every occurrence, use the erase-remove idiom:

s.erase(std::remove(s.begin(), s.end(), 'a'), s.end());

Remove by Position

#include <iostream>
#include <string>

int main() {
    std::string s = "hello";

    s.erase(1, 1);        // remove 1 char at index 1
    std::cout << s;       // hllo
}

erase(pos, count) removes count characters starting at pos. Leave off the count and it removes everything from that position onward:

std::string s = "hello world";
s.erase(5);               // hello

Passing an index beyond the end throws std::out_of_range, so validate first if the index comes from user input or a search.

Remove the First or Last Character

std::string s = "hello";

s.pop_back();             // hell     (C++11)
s.erase(0, 1);            // ell

pop_back() on an empty string is undefined behaviour — no exception, just silent corruption. Always guard it:

if (!s.empty()) s.pop_back();

Remove Every Occurrence: The Erase-Remove Idiom

This is the one people search for:

#include <algorithm>
#include <iostream>
#include <string>

int main() {
    std::string s = "banana";

    s.erase(std::remove(s.begin(), s.end(), 'a'), s.end());

    std::cout << s;       // bnn
}

It looks strange until you see what each half does.

Why std::remove Does Not Remove

std::remove works through iterators, and iterators cannot resize a container. So it does the only thing it can: it shuffles the characters you want to keep towards the front, and returns an iterator marking the new logical end.

std::string s = "banana";
auto newEnd = std::remove(s.begin(), s.end(), 'a');

// s is now "bnn" + 3 leftover characters
// s.size() is still 6

The leftover tail is unspecified junk. erase(newEnd, s.end()) chops it off and fixes the size. That is why the two calls are always written together — using remove alone is a classic bug that leaves a string looking right when printed but reporting the wrong length.

Remove Characters Matching a Rule

remove_if takes a predicate instead of a value:

#include <algorithm>
#include <cctype>

// remove all whitespace, not just spaces
s.erase(std::remove_if(s.begin(), s.end(),
        [](unsigned char c){ return std::isspace(c); }), s.end());

// keep only letters and digits
s.erase(std::remove_if(s.begin(), s.end(),
        [](unsigned char c){ return !std::isalnum(c); }), s.end());

// remove all digits
s.erase(std::remove_if(s.begin(), s.end(),
        [](unsigned char c){ return std::isdigit(c); }), s.end());

The unsigned char cast is not optional pedantry. Passing a negative char to isspace is undefined behaviour, and it genuinely crashes on some inputs with accented characters.

Remove the First Occurrence Only

std::string s = "banana";
size_t pos = s.find('a');
if (pos != std::string::npos) {
    s.erase(pos, 1);
}
std::cout << s;          // bnana

Always check for npos — passing it to erase throws.

C++20: std::erase and std::erase_if

C++20 finally added the obvious spelling:

#include <string>

std::string s = "banana";
std::erase(s, 'a');                                  // bnn

std::erase_if(s, [](char c){ return c == 'n'; });    // b

Same behaviour, no iterator pair, no chance of forgetting the erase half. Use it if your compiler supports C++20.

Removing from a Vector Works the Same Way

The idiom is not string-specific:

std::vector<int> v = {1, 2, 3, 2, 4};
v.erase(std::remove(v.begin(), v.end(), 2), v.end());
// 1 3 4

See removing elements from a vector for the container version and its iterator traps.

Quick Reference

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Related Articles

• How to Trim Whitespace from a String in C++ — removing only the ends.
• How to Replace a Substring in a C++ String — swapping text instead of deleting it.
• How to Remove an Element from a Vector — the same idiom on containers.
• C++ String Handling: A Complete Guide — the wider picture.
• How to Check if a String Contains a Substring — finding before removing.