ureq/README.md

[comment]: # (README.md is autogenerated from src/lib.rs by `cargo readme > README.md`)

# ureq

A simple, safe HTTP client.

Ureq's first priority is being easy for you to use. It's great for
anyone who wants a low-overhead HTTP client that just gets the job done. Works
very well with HTTP APIs. Its features include cookies, JSON, HTTP proxies,
HTTPS, and charset decoding.

Ureq is in pure Rust for safety and ease of understanding. It avoids using
`unsafe` directly. It [uses blocking I/O][blocking] instead of async I/O, because that keeps
the API simple and and keeps dependencies to a minimum. For TLS, ureq uses
[rustls or native-tls](#tls).

Version 2.0.0 was released recently and changed some APIs. See the [changelog] for details.

[blocking]: #blocking-io-for-simplicity
[changelog]: https://github.com/algesten/ureq/blob/master/CHANGELOG.md


### Usage

In its simplest form, ureq looks like this:

```rust
fn main() -> Result<(), ureq::Error> {
    let body: String = ureq::get("http://example.com")
        .set("Example-Header", "header value")
        .call()?
        .into_string()?;
    Ok(())
}
```

For more involved tasks, you'll want to create an [Agent]. An Agent
holds a connection pool for reuse, and a cookie store if you use the
"cookies" feature. An Agent can be cheaply cloned due to an internal
[Arc](std::sync::Arc) and all clones of an Agent share state among each other. Creating
an Agent also allows setting options like the TLS configuration.

```rust
  use ureq::{Agent, AgentBuilder};
  use std::time::Duration;

  let agent: Agent = ureq::AgentBuilder::new()
      .timeout_read(Duration::from_secs(5))
      .timeout_write(Duration::from_secs(5))
      .build();
  let body: String = agent.get("http://example.com/page")
      .call()?
      .into_string()?;

  // Reuses the connection from previous request.
  let response: String = agent.put("http://example.com/upload")
      .set("Authorization", "example-token")
      .call()?
      .into_string()?;
```

Ureq supports sending and receiving json, if you enable the "json" feature:

```rust
  // Requires the `json` feature enabled.
  let resp: String = ureq::post("http://myapi.example.com/ingest")
      .set("X-My-Header", "Secret")
      .send_json(ureq::json!({
          "name": "martin",
          "rust": true
      }))?
      .into_string()?;
```

### Error handling

ureq returns errors via `Result<T, ureq::Error>`. That includes I/O errors,
protocol errors, and status code errors (when the server responded 4xx or
5xx)

```rust
use ureq::Error;

match ureq::get("http://mypage.example.com/").call() {
    Ok(response) => { /* it worked */},
    Err(Error::Status(code, response)) => {
        /* the server returned an unexpected status
           code (such as 400, 500 etc) */
    }
    Err(_) => { /* some kind of io/transport error */ }
}
```

More details on the [Error] type.

### Features

To enable a minimal dependency tree, some features are off by default.
You can control them when including ureq as a dependency.

`ureq = { version = "*", features = ["json", "charset"] }`

* `tls` enables https. This is enabled by default.
* `native-certs` makes the default TLS implementation use the OS' trust store (see TLS doc below).
* `cookies` enables cookies.
* `json` enables [Response::into_json()] and [Request::send_json()] via serde_json.
* `charset` enables interpreting the charset part of the Content-Type header
   (e.g.  `Content-Type: text/plain; charset=iso-8859-1`). Without this, the
   library defaults to Rust's built in `utf-8`.
* `socks-proxy` enables proxy config using the `socks4://`, `socks4a://`, `socks5://` and `socks://` (equal to `socks5://`) prefix.
* `native-tls` enables an adapter so you can pass a `native_tls::TlsConnector` instance
  to `AgentBuilder::tls_connector`. Due to the risk of diamond dependencies accidentally switching on an unwanted
  TLS implementation, `native-tls` is never picked up as a default or used by the crate level
  convenience calls (`ureq::get` etc) – it must be configured on the agent. The `native-certs` feature
  does nothing for `native-tls`.

## Plain requests

Most standard methods (GET, POST, PUT etc), are supported as functions from the
top of the library ([get()], [post()], [put()], etc).

These top level http method functions create a [Request] instance
which follows a build pattern. The builders are finished using:

* [`.call()`][Request::call()] without a request body.
* [`.send()`][Request::send()] with a request body as [Read][std::io::Read] (chunked encoding support for non-known sized readers).
* [`.send_string()`][Request::send_string()] body as string.
* [`.send_bytes()`][Request::send_bytes()] body as bytes.
* [`.send_form()`][Request::send_form()] key-value pairs as application/x-www-form-urlencoded.

## JSON

By enabling the `ureq = { version = "*", features = ["json"] }` feature,
the library supports serde json.

* [`request.send_json()`][Request::send_json()] send body as serde json.
* [`response.into_json()`][Response::into_json()] transform response to json.

## Content-Length and Transfer-Encoding

The library will send a Content-Length header on requests with bodies of
known size, in other words, those sent with
[`.send_string()`][Request::send_string()],
[`.send_bytes()`][Request::send_bytes()],
[`.send_form()`][Request::send_form()], or
[`.send_json()`][Request::send_json()]. If you send a
request body with [`.send()`][Request::send()],
which takes a [Read][std::io::Read] of unknown size, ureq will send Transfer-Encoding:
chunked, and encode the body accordingly. Bodyless requests
(GETs and HEADs) are sent with [`.call()`][Request::call()]
and ureq adds neither a Content-Length nor a Transfer-Encoding header.

If you set your own Content-Length or Transfer-Encoding header before
sending the body, ureq will respect that header by not overriding it,
and by encoding the body or not, as indicated by the headers you set.

```rust
let resp = ureq::post("http://my-server.com/ingest")
    .set("Transfer-Encoding", "chunked")
    .send_string("Hello world");
```

## Character encoding

By enabling the `ureq = { version = "*", features = ["charset"] }` feature,
the library supports sending/receiving other character sets than `utf-8`.

For [`response.into_string()`][Response::into_string()] we read the
header `Content-Type: text/plain; charset=iso-8859-1` and if it contains a charset
specification, we try to decode the body using that encoding. In the absence of, or failing
to interpret the charset, we fall back on `utf-8`.

Similarly when using [`request.send_string()`][Request::send_string()],
we first check if the user has set a `; charset=<whatwg charset>` and attempt
to encode the request body using that.


## Proxying

ureq supports two kinds of proxies,  HTTP [`CONNECT`], [`SOCKS4`] and [`SOCKS5`], the former is
always available while the latter must be enabled using the feature
`ureq = { version = "*", features = ["socks-proxy"] }`.

Proxies settings are configured on an [Agent] (using [AgentBuilder]). All request sent
through the agent will be proxied.

### Example using HTTP CONNECT

```rust
fn proxy_example_1() -> std::result::Result<(), ureq::Error> {
    // Configure an http connect proxy. Notice we could have used
    // the http:// prefix here (it's optional).
    let proxy = ureq::Proxy::new("user:password@cool.proxy:9090")?;
    let agent = ureq::AgentBuilder::new()
        .proxy(proxy)
        .build();

    // This is proxied.
    let resp = agent.get("http://cool.server").call()?;
    Ok(())
}
```

### Example using SOCKS5

```rust
fn proxy_example_2() -> std::result::Result<(), ureq::Error> {
    // Configure a SOCKS proxy.
    let proxy = ureq::Proxy::new("socks5://user:password@cool.proxy:9090")?;
    let agent = ureq::AgentBuilder::new()
        .proxy(proxy)
        .build();

    // This is proxied.
    let resp = agent.get("http://cool.server").call()?;
    Ok(())
}
```

## HTTPS / TLS / SSL

On platforms that support rustls, ureq uses rustls. On other platforms, native-tls can
be manually configured using [`AgentBuilder::tls_connector`].

You might want to use native-tls if you need to interoperate with servers that
only support less-secure TLS configurations (rustls doesn't support TLS 1.0 and 1.1, for
instance). You might also want to use it if you need to validate certificates for IP addresses,
which are not currently supported in rustls.

Here's an example of constructing an Agent that uses native-tls. It requires the
"native-tls" feature to be enabled.

```rust
  use std::sync::Arc;
  use ureq::Agent;

  let agent = ureq::AgentBuilder::new()
      .tls_connector(Arc::new(native_tls::TlsConnector::new().unwrap()))
      .build();
```

### Trusted Roots

When you use rustls (`tls` feature), ureq defaults to trusting
[webpki-roots](https://docs.rs/webpki-roots/), a
copy of the Mozilla Root program that is bundled into your program (and so won't update if your
program isn't updated). You can alternately configure
[rustls-native-certs](https://docs.rs/rustls-native-certs/) which extracts the roots from your
OS' trust store. That means it will update when your OS is updated, and also that it will
include locally installed roots.

When you use `native-tls`, ureq will use your OS' certificate verifier and root store.

## Blocking I/O for simplicity

Ureq uses blocking I/O rather than Rust's newer [asynchronous (async) I/O][async]. Async I/O
allows serving many concurrent requests without high costs in memory and OS threads. But
it comes at a cost in complexity. Async programs need to pull in a runtime (usually
[async-std] or [tokio]). They also need async variants of any method that might block, and of
[any method that might call another method that might block][what-color]. That means async
programs usually have a lot of dependencies - which adds to compile times, and increases
risk.

The costs of async are worth paying, if you're writing an HTTP server that must serve
many many clients with minimal overhead. However, for HTTP _clients_, we believe that the
cost is usually not worth paying. The low-cost alternative to async I/O is blocking I/O,
which has a different price: it requires an OS thread per concurrent request. However,
that price is usually not high: most HTTP clients make requests sequentially, or with
low concurrency.

That's why ureq uses blocking I/O and plans to stay that way. Other HTTP clients offer both
an async API and a blocking API, but we want to offer a blocking API without pulling in all
the dependencies required by an async API.

[async]: https://rust-lang.github.io/async-book/01_getting_started/02_why_async.html
[async-std]: https://github.com/async-rs/async-std#async-std
[tokio]: https://github.com/tokio-rs/tokio#tokio
[what-color]: https://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/
[`CONNECT`]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/CONNECT
[`SOCKS4`]: https://en.wikipedia.org/wiki/SOCKS#SOCKS4
[`SOCKS5`]: https://en.wikipedia.org/wiki/SOCKS#SOCKS5

------------------------------------------------------------------------------

Ureq is inspired by other great HTTP clients like
[superagent](http://visionmedia.github.io/superagent/) and
[the fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API).

If ureq is not what you're looking for, check out these other Rust HTTP clients:
[surf](https://crates.io/crates/surf), [reqwest](https://crates.io/crates/reqwest),
[isahc](https://crates.io/crates/isahc), [attohttpc](https://crates.io/crates/attohttpc),
[actix-web](https://crates.io/crates/actix-web), and [hyper](https://crates.io/crates/hyper).


[rustls]: https://docs.rs/rustls/
[std::sync::Arc]: https://doc.rust-lang.org/stable/alloc/sync/struct.Arc.html
[std::io::Read]: https://doc.rust-lang.org/stable/std/io/trait.Read.html
[Agent]: https://docs.rs/ureq/latest/ureq/struct.Agent.html
[get()]: https://docs.rs/ureq/latest/ureq/fn.get.html
[post()]: https://docs.rs/ureq/latest/ureq/fn.post.html
[put()]: https://docs.rs/ureq/latest/ureq/fn.put.html
[Request]: https://docs.rs/ureq/latest/ureq/struct.Request.html
[Error]: https://docs.rs/ureq/latest/ureq/enum.Error.html
[Request::call()]: https://docs.rs/ureq/latest/ureq/struct.Request.html#method.call
[Request::send()]: https://docs.rs/ureq/latest/ureq/struct.Request.html#method.send
[Request::send_bytes()]: https://docs.rs/ureq/latest/ureq/struct.Request.html#method.send_bytes
[Request::send_string()]: https://docs.rs/ureq/latest/ureq/struct.Request.html#method.send_string
[Request::send_json()]: https://docs.rs/ureq/latest/ureq/struct.Request.html#method.send_json
[Request::send_form()]: https://docs.rs/ureq/latest/ureq/struct.Request.html#method.send_form
[Response::into_json()]: https://docs.rs/ureq/latest/ureq/struct.Response.html#method.into_json
[Response::into_string()]: https://docs.rs/ureq/latest/ureq/struct.Response.html#method.into_string