urllib3 vs Requests: Differences & Best Use Cases

HTTP libraries are critical for interacting with the web. They let you send and receive data via HTTP requests. In Python, making requests is common in tasks like web scraping, API calls, and automation.

If you’re comparing urllib3 vs requests to see which HTTP client library fits your needs best, start by looking into their basic differences. Understanding things like syntax, code readability, performance, safety, error-handling, and HTTP support will let you make the decision faster.

What is urllib3?

urllib3 is a third-party HTTP client library for Python that replaces and extends the capabilities of the built-in urllib modules in a user-friendly way. It’s not included in Python’s standard library, so you must install it separately using the pip command.

It’s worth using urllib3 as it offers a more robust connection pooling, thread safety, and control over SSL verification. At the same time, it’s still a lightweight third-party library for handling HTTP connections.

Main features:

• Connection pooling to reuse TCP connections efficiently.
• Low-level control of request headers, timeouts, and retries.
• Explicit SSL/TLS verification settings.

A sample code using urllib3 would look like this:

import urllib3

http = urllib3.PoolManager()
response = http.request(
    "GET",
    "https://httpbin.org",
    headers={"User-Agent": "urllib3-client"}
)
print(response.status, response.data[:100])
response.release_conn()

What is requests?

Requests is one of the most popular third-party libraries for making HTTP requests in Python. The requests library has simple, human-readable syntax and powerful features like sessions, authentication, file uploads, and JSON handling.

Many use the requests library for web scraping , API calls, and web automation. Requests is designed to be human-friendly, feeling like ordinary Python code instead of low-level networking, while rich in HTTP and proxy features.

Main features:

• Session objects manage cookies, TCP connections, and headers across multiple requests.
• First-class support for redirects, timeouts, streaming downloads, file uploads (multipart), and proxies.
• Simple functions ensure clear applications that fit into existing Python code easily.

Here's sample code made with the requests library:

import requests

response = requests.get(
    "https://httpbin.org",
    headers={"User-Agent": "python-requests"}
)
print(response.status_code, response.text[:100])

How urllib3 and requests Are Related

Requests is built on top of urllib3 and uses it as the underlying HTTP engine. It was developed later to wrap urllib3 with a simpler and more user-friendly Python development environment. It's the reason why installing requests automatically installs urllib3 as well.

Think about requests as a vehicle and urllib3 as the engine. The vehicle's control features allow you to travel without tinkering with the engine, but you can do it if needed. Similarly, most developers rely on requests, but in some cases, you might need fine-grained control over the transport layer.

Key Differences Between urllib3 and requests

1. Syntax & Readability

• urllib3: More verbose and low-level. You handle details like response decoding and JSON parsing manually.
• requests: Clean and intuitive, which is ideal for beginners and quick scripts.

2. Performance & Features

• urllib3: Great connection pooling, lightweight. Requires explicit retry configuration using the Retry utility class.
• requests: Built on urllib3, adds convenience features like automatic JSON parsing, session management, and a simpler timeout API.

3. Thread-Safety & Error Handling

• urllib3: Thread-safe, but you handle exceptions and retries yourself.
• requests: Provides a cleaner exception hierarchy and simpler error handling patterns.

4. HTTP Support (GET, POST Handling)

• urllib3 and requests: Both support sending HTTP requests via GET, POST, and more.
• requests: Supports multipart form, file uploads, and making HTTP requests with ease.

Performance & Scalability Considerations

For large production systems or high-volume applications, performance and scalability factors come into play. Generally, for APIs or moderate-scale scraping, the requests library offers the best balance as it's less demanding of developers.

However, when performance requirements are even larger, and one needs to maximize the output with minimal resources, urllib3 might be preferred. The added development complexity is often justified by the lower-level controls and slightly reduced overhead. In the end, it's a strategic decision, based on several factors.

• Connection pooling. Both libraries support pooling, but with different levels of control. urllib3 gives more control with explicit PoolManager configurations, while requests handles pooling automatically with Session objects.
• Overhead and raw speed. urllib3 is slightly faster as there's no intermediate layer between the code and the HTTP engine. Given the ease of development it brings, the requests library wrapper is still quite lightweight.
• Resource management. You must decide whether you want to manage resources manually or automatically. Long-running or memory-constrained environments benefit from urllib3's explicit connection management, but in other cases, requests simplicity is advantageous.
• Custom headers. Both libraries handle headers efficiently, but requests make it easier to keep persistent headers via Session.headers. urllib3 requires passing headers explicitly on each request, creating more lines of code.
• Cookie handling. Scalability is better with requests due to the fact that Session objects manage cookies automatically across requests. With urllib3, you must manually work with set-Cookie headers, which adds code complexity.
• Multi-threading. The requests library inherits thread-safety from urllib3's connection pools, but each thread typically uses its own Session object to avoid headers and cookie conflicts. The biggest difference is that urllib3's explicit control makes threading behavior more transparent.

When to Use urllib3

When you need direct control over the transport layer or are building infrastructure that must be efficient, use urllib3. This is often the case in a few common development scenarios:

• For low-level control, high-performance, and advanced connection pooling.
• When building for libraries and background services.
• If you're building a large-scale service or framework, you might use urllib3 as the foundation while using requests for simpler, higher-level HTTP tasks.

When to Use requests

You use Python's requests when your priority is developer productivity, code readability, and standard web interactions. It is the default choice for everything except high-performance infrastructure or library development.

• When ease of use, quick scripts, and web scraping convenience are a priority.
• If you need automatic session cookie handling and authentication.
• For larger projects, you may need to use both urllib3 and requests side-by-side.

When to Consider Alternatives (HTTPX, aiohttp)

Alternatives to requests and urllib3 should be considered when your scraper or application needs to send asynchronous requests. Both HTTP clients are synchronous, forcing the program to wait for each response or manage complex threading operations sequentially.

We have previously covered how requests compare against HTTPX and aiohttp . There are some cases when alternatives might change your decision between urllib3 and requests.

• HTTPX is designed as a requests-compatible library supporting both synchronous and asynchronous operations with HTTP/2. It provides httpx.Client() for traditional synchronous code and httpx.AsyncClient() for async workflows, giving more flexibility as you can migrate or mix both behaviors in the same code.
• aiohttp is built from the ground up to be async-only. It also includes a full-featured web server framework, useful for async web applications and other use cases. The tradeoff is a steeper learning curve and the need to build your entire application async-only.

Most developers can stay with requests and urllib3, especially when building simple scripts, when the complexity of adding async cannot be fully justified. Using HTTPX or aiohttp requires significant commitment, which might complicate code maintenance in the long term.

How to Install and Use Each Library

Installing urllib3 or the requests library is quite similar because, as with most libraries, they can be installed with pip commands. The immediate differences you'll notice when using them are in handling retries, errors, and sending HTTP requests.

Installing urllib3

You can install the standalone version or urllib3 with:

pip install urllib3

Note that Python's standard library includes urllib.request, but urllib3 is a separate third-party library offering more advanced features.

urllib3 Request Example

import urllib3
from urllib3.exceptions import HTTPError

http = urllib3.PoolManager()

try:
    response = http.request(
        "GET",
        "https://httpbin.org",
        headers={"User-Agent": "custom-client"}
    )
    print(response.status, response.data[:100])  # response data snippet
except HTTPError as e:
    print("Request failed:", e)

Installing requests

To install the requests library, run the following pip command:

pip install requests

It's one of the easiest ways to start making HTTP requests and handling response data quickly. Installing requests also sets up urllib3 as its dependency.

requests Example With Retry

import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

session = requests.Session()
retry = Retry(
    total=3,
    backoff_factor=0.3,
    status_forcelist=[500, 502, 503, 504]
)
adapter = HTTPAdapter(max_retries=retry)
session.mount("https://", adapter)

try:
    resp = session.get("https://httpbin.org")
    print(resp.status_code, resp.text[:100])
except requests.RequestException as e:
    print("Request failed:", e)

Conclusion

Choosing between urllib3 vs requests comes down to the level of control you need and how complex your project is. If you're dealing with large-scale web scraping, parallel tasks, or long-running jobs, explore both urllib3 and requests.

For smaller projects, small-scale web scraping, or beginner-level learning, Python's requests offers a more user-friendly experience.

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