Ada 2.9.0
Fast spec-compliant URL parser
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Ada is a fast and spec-compliant URL parser written in C++. Specification for URL parser can be found from the WHATWG website.

The Ada library passes the full range of tests from the specification, across a wide range of platforms (e.g., Windows, Linux, macOS). It fully supports the relevant Unicode Technical Standard.

A common use of a URL parser is to take a URL string and normalize it. The WHATWG URL specification has been adopted by most browsers. Other tools, such as curl and many standard libraries, follow the RFC 3986. The following table illustrates possible differences in practice (encoding of the host, encoding of the path):

string source string value
input string https://www.7‑éal
ada's normalized string https://www.xn–
curl 7.87 (returns the original unchanged)


The project is otherwise self-contained and it has no dependency. A recent C++ compiler supporting C++17. We test GCC 9 or better, LLVM 10 or better and Microsoft Visual Studio 2022.

Ada is fast.

On a benchmark where we need to validate and normalize thousands URLs found on popular websites, we find that ada can be several times faster than popular competitors (system: Apple MacBook 2022 with LLVM 14).

ada ▏ 188 ns/URL ███▏
servo url ▏ 664 ns/URL ███████████▎
CURL ▏ 1471 ns/URL █████████████████████████

Ada has improved the performance of the popular JavaScript environment Node.js:

‍Since Node.js 18, a new URL parser dependency was added to Node.js — Ada. This addition bumped the Node.js performance when parsing URLs to a new level. Some results could reach up to an improvement of 400%. (State of Node.js Performance 2023)

The Ada library is used by important systems besides Node.js such as Redpanda and Cloudflare Workers.

the ada library

Quick Start

Linux or macOS users might follow the following instructions if they have a recent C++ compiler installed and a standard utility (wget)

  1. Pull the library in a directory
  2. Create a new file named demo.cpp with this content:
    #include "ada.cpp"
    #include "ada.h"
    #include <iostream>
    int main(int, char *[]) {
    auto url = ada::parse<ada::url>("");
    if (!url) {
    std::cout << "failure" << std::endl;
    return EXIT_FAILURE;
    std::cout << url->get_protocol() << std::endl;
    std::cout << url->get_host() << std::endl;
    return EXIT_SUCCESS;
    Includes all definitions for Ada.
    ada_warn_unused ada::result< result_type > parse(std::string_view input, const result_type *base_url=nullptr)
  1. Compile
    c++ -std=c++17 -o demo demo.cpp
  2. ./demo


Bindings of Ada

We provide clients for different programming languages through our C API.

  • Rust: Rust bindings for Ada
  • Go: Go bindings for Ada
  • Python: Python bindings for Ada
  • R: R wrapper for Ada


Ada supports two types of URL instances, ada::url and ada::url_aggregator. The usage is the same in either case: we have an parsing function template ada::parse which can return either a result of type ada::result<ada::url> or of type ada::result<ada::url_aggregator> depending on your needs. The ada::url_aggregator class is smaller and it is backed by a precomputed serialized URL string. The ada::url class is made of several separate strings for the various components (path, host, and so forth).

Parsing & Validation

  • Parse and validate a URL from an ASCII or a valid UTF-8 string.
if (url) { /* URL is valid */ }
tl::expected< result_type, ada::errors > result

After calling 'parse', you must check that the result is valid before accessing it when you are not sure that it will succeed. The following code is unsafe:


You should do...

if(url) {
// next line is now safe:
} else {
// report a parsing failure

For simplicity, in the examples below, we skip the check because we know that parsing succeeds. All strings are assumed to be valid UTF-8 strings.


  • Get/Update credentials
// ada->get_href() will return "https://username:[email protected]/"
  • Get/Update Protocol
// url->get_protocol() will return "wss:"
// url->get_href() will return "wss://"
  • Get/Update host
// url->get_host() will return ""
// you can use `url.set_hostname` depending on your usage.
  • Get/Update port
// url->get_port() will return "8080"
  • Get/Update pathname
// url->get_pathname() will return "/my-super-long-path"
  • Get/Update search/query
// url->get_search() will return "?target=self"
  • Get/Update hash/fragment
// url->get_hash() will return "#is-this-the-real-life"

For more information about command-line options, please refer to the CLI documentation.

  • URL search params
ada::url_search_params search_params("a=b&c=d&e=f");
search_params.get("g"); // will return "h"
auto keys = search_params.get_keys();
while (keys.has_next()) {
auto key =; // "a", "c", "e", "g"

C wrapper

See the file include/ada_c.h for our C interface. We expect ASCII or UTF-8 strings.

#include "ada_c.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
static void ada_print(ada_string string) {
printf("%.*s\n", (int)string.length,;
int main(int c, char *arg[] ) {
const char* input =
"https://username:[email protected]:8080/"
ada_url url = ada_parse(input, strlen(input));
if(!ada_is_valid(url)) { puts("failure"); return EXIT_FAILURE; }
ada_print(ada_get_href(url)); // prints https://username:password@host:8080/pathname?query=true#hash-exists
ada_print(ada_get_protocol(url)); // prints https:
ada_print(ada_get_username(url)); // prints username
ada_set_href(url, "", strlen(""));
if(!ada_is_valid(url)) { puts("failure"); return EXIT_FAILURE; }
ada_set_hash(url, "new-hash", strlen("new-hash"));
ada_set_hostname(url, "new-host", strlen("new-host"));
ada_set_host(url, "changed-host:9090", strlen("changed-host:9090"));
ada_set_pathname(url, "new-pathname", strlen("new-pathname"));
ada_set_search(url, "new-search", strlen("new-search"));
ada_set_protocol(url, "wss", 3);
ada_print(ada_get_href(url)); // will print wss://changed-host:9090/new-pathname?new-search#new-hash
// Manipulating search params
ada_string search = ada_get_search(url);
ada_url_search_params search_params =
ada_search_params_append(search_params, "a", 1, "b", 1);
ada_set_search(url,, result.length);
Includes the C definitions for Ada. This is a C file, not C++.
ada_url_search_params ada_parse_search_params(const char *input, size_t length)
Definition ada_c.cpp:466
bool ada_set_host(ada_url result, const char *input, size_t length)
Definition ada_c.cpp:244
void ada_search_params_append(ada_url_search_params result, const char *key, size_t key_length, const char *value, size_t value_length)
Definition ada_c.cpp:515
bool ada_set_hostname(ada_url result, const char *input, size_t length)
Definition ada_c.cpp:252
void ada_free_search_params(ada_url_search_params result)
Definition ada_c.cpp:472
bool ada_set_pathname(ada_url result, const char *input, size_t length)
Definition ada_c.cpp:296
void * ada_url_search_params
Definition ada_c.h:113
ada_url ada_parse(const char *input, size_t length)
Definition ada_c.cpp:67
void ada_free_owned_string(ada_owned_string owned)
Definition ada_c.cpp:126
ada_owned_string ada_search_params_to_string(ada_url_search_params result)
Definition ada_c.cpp:477
bool ada_set_href(ada_url result, const char *input, size_t length)
Definition ada_c.cpp:236
void ada_free(ada_url result)
Definition ada_c.cpp:95
void * ada_url
Definition ada_c.h:39
ada_string ada_get_protocol(ada_url result)
Definition ada_c.cpp:211
ada_string ada_get_username(ada_url result)
Definition ada_c.cpp:139
bool ada_is_valid(ada_url result)
Definition ada_c.cpp:105
void ada_set_search(ada_url result, const char *input, size_t length)
Definition ada_c.cpp:312
ada_string ada_get_href(ada_url result)
Definition ada_c.cpp:130
bool ada_set_protocol(ada_url result, const char *input, size_t length)
Definition ada_c.cpp:261
ada_string ada_get_search(ada_url result)
Definition ada_c.cpp:202
void ada_set_hash(ada_url result, const char *input, size_t length)
Definition ada_c.cpp:326
const char * data
Definition ada_c.h:18
size_t length
Definition ada_c.h:19

When linking against the ada library from C++, be minding that ada requires access to the standard C++ library. E.g., you may link with the C++ compiler.

E.g., if you grab our single-header C++ files (ada.cpp and ada.h), as well as the C header (ada_c.h), you can often compile a C program (demo.c) as follows under Linux/macOS systems:

c++ -c ada.cpp -std=c++17
cc -c demo.c
c++ demo.o ada.o -o cdemo

CMake dependency

See the file tests/installation/CMakeLists.txt for an example of how you might use ada from your own CMake project, after having installed ada on your system.



Ada is available through Homebrew. You can install Ada using brew install ada-url.



Ada uses cmake as a build system. It's recommended you to run the following commands to build it locally.

  • Build: cmake -B build && cmake --build build
  • Test: ctest --output-on-failure --test-dir build

Windows users need additional flags to specify the build configuration, e.g. --config Release.

The project can also be built via docker using default docker file of repository with following commands.

docker build -t ada-builder . && docker run --rm -it -v ${PWD}:/repo ada-builder


You may amalgamate all source files into only two files (ada.h and ada.cpp) by typing executing the Python 3 script singleheader/ By default, the files are created in the singleheader directory.


This code is made available under the Apache License 2.0 as well as the MIT license.

Our tests include third-party code and data. The benchmarking code includes third-party code: it is provided for research purposes only and not part of the library.

Further reading