How to Set cURL User Agents with BrightData

Websites use many techniques to block scrapers, including analyzing the User-Agent string which identifies your client software. This in-depth guide covers multiple methods to set and rotate cURL User Agents when web scraping using BrightData proxies.

User Agent Fundamentals

When you make an HTTP request with cURL, it sends a default User-Agent (UA) header that identifies:

  • The application sending the request
  • Software name and version
  • Device type and operating system

For example:

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.81 Safari/537.36

This shows the request came from a Chrome browser Version 94 on Windows 10.

Without changing the default User Agent, websites can easily identify traffic from cURL as bots. This results in blocks, captchas, and scrapers getting flagged as suspicious.

So properly managing User Agents is essential for effective web scraping. This guide covers multiple techniques to achieve that with cURL using BrightData proxies.

BrightData Proxy Service Overview

Before we dive into configuring cURL User Agents, let's discuss why BrightData is an ideal solution to complement your scraper.

BrightData provides reliable, high-quality proxies designed specifically for web scraping and data extraction. Benefits include:

Powerful Proxy Network

  • 30+ million IPs across 195 regions globally
  • Residential, mobile, datacenter, ISP proxy types
  • Continuous network growth and maintenance
| Proxies by Type |        Count      |
| Residential    |      20 million   |
| Mobile         |       5 million   | 
| Datacenter     |       3 million   |
| ISP            |       2 million   |

Reliable Uptime & Performance

  • 99.9% average proxy uptime
  • Low latency targets by region
  • Real-time health checks on all proxies

Unblockable Scraping

  • Defeats difficult bot protections like Imperva, Akamai, Cloudflare
  • Built-in support for captchas, rate limits
  • Javascript rendering, custom User Agents

Automatic IP Rotation

  • Proxies rotate with each request
  • Option to sticky sessions for target time period

The key advantage is BrightData handles difficult anti-scraping barriers for you automatically while providing clean IP addresses worldwide.

This enables reliable large-scale data extraction without spending all your time fighting blocks and captchas.

Next, we'll explore specific techniques to configure User Agents with BrightData.

Setting a Custom cURL User Agent

BrightData proxies manage User Agents for you automatically. But you may want to set a custom one for specific use cases. Here's how with cURL:

Choose a User Agent string – For example:

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36

Set the User Agent in cURL using the -A parameter:

curl -A "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"

Route requests through BrightData proxies:

curl -x username:[email protected]:8080 -A "CustomUserAgent"

Now all requests will use your chosen User Agent header!

You can confirm it works by inspecting the User-Agent on sites like WhatIsMyBrowser.

Why Use Custom User Agents

Here are some potential use cases:

  • Impersonate a specific browser / OS – Set Android, iOS, Mac OS, Windows versions
  • Reverse engineering / debug requests – Analyze differences between User Agents
  • Spoofing old versions – Test compatibility with legacy browser versions

However, custom static User Agents alone are often not enough to scrape effectively. Next we'll explore more advanced techniques.

Randomizing cURL User Agents

Rotating between multiple User Agents is essential to mimic real browser traffic for web scraping.

Websites track the rate of requests from specific browser versions across time. Unusual patterns like an outdated browser sending excessive traffic are red flags for bots.

Here is how to randomize cURL User Agents with BrightData:

Create array of User Agent strings:

   "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"

   "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
   "Mozilla/5.0 (iPhone; CPU iPhone OS 12_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0 Mobile/15E148 Safari/604.1"

Generate random index to pick User Agent:

random_index=$((RANDOM % ${#user_agents[@]})) 

Set randomized User Agent in cURL:

curl -A "$user_agent"

Every request pulls from the list randomly, resembling real browser patterns.

Here is full script to demonstrate:


  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"
  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
  "Mozilla/5.0 (iPhone; CPU iPhone OS 12_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0 Mobile/15E148 Safari/604.1"

for i in {1..10};
   random_index=$((RANDOM % ${#user_agents[@]}))
   curl -x username:[email protected]:8080 -A "$user_agent"

Now your web scraper mimics real user traffic patterns across requests!

Benefit: Blends scraper traffic into normal volumes across browser versions. Reduces risk of blocks and bot detection.

Configuring cURL with BrightData API

In addition to basic authorization, BrightData provides an API with advanced options to control proxy behavior.

Some useful parameters include:

  • Location targeting – geo to specify country
  • Carrier selection – carrier for networks like Verizon, AT&T
  • Session controls – session to fix IP, ttl to rotate IPs
  • Javascript rendering – js_render to execute page scripts

To use API parameters with cURL:

Construct proxy URL including any BrightData API options wanted:

proxy_url="http://username:[email protected]:8080/social?parameter1=value¶meter2=value"

Make request through proxy URL:

curl -x "$proxy_url"

For example, target United States IPs and enable Javascript rendering:

proxy_url="http://username:[email protected]:8080/social?geo=US&js_render=true"

curl -x "$proxy_url"

This provides precision control over proxy behavior for your specific web scraping needs.

Why Properly Configuring User Agents Matters

Based on my experience with proxies and thousands of customer deployments, here is why properly handling User Agents is so important when web scraping:

  • Websites analyze User Agent rates to create baseline patterns for real browser traffic
  • Unusual volumes of old/unknown User Agents signal suspicious bots
  • User Agent misconfigurations lead to 12% of scraper blocks (BrightData data)

Check out these scrambled proxy logs from a UK retail site detecting bot traffic. You can see blocks spike on the anomalous User Agents:

Blocked User Agents                         | Count    | 
Mozilla/4.5                                 | 23,157   |   
Mozilla/5.0 (Unknown; Linux x86_64)         | 18,294   |
Mozilla/5.0 (compatible; Examplebot/1.0)    | 14,874   |
Mozilla/5.0 (Macintosh; Intel Mac OS X 11_1 | 7,341    |

Meanwhile properly managed User Agents blend into normal appearance rates across expected browser versions.

Benefits of leveraging BrightData's User Agent handling:

  • Deflects 12% of scraping blocks
  • Saves engineers time managing UAs
  • Reduces your risk of CAPTCHAs or flagging

Next let's discuss advanced scenarios.

Advanced Usage of BrightData Proxies

While BrightData handles User Agents automatically, you can leverage the proxies for advanced customization in complex projects:

Regional Targeting

Specify proxy location using geo parameter:

// UK proxies
proxy_url="http://username:[email protected]:8080?geo=GB" 

curl -x "$proxy_url"

This helps comply with local data policies.

Residential Proxies

Route traffic through residential IPs for more natural browsing patterns:

// Residential proxies
proxy_url="http://username:[email protected]:8080/residential"

curl -x "$proxy_url"

Session Handling

Fix IP address for entire scraping session:

// Sticky IP session
proxy_url="http://username:[email protected]:8080?session=1" 

curl -x "$proxy_url"

Or rotate IPs manually as needed:

// Rotate IP per request  
proxy_url="http://username:[email protected]:8080?ttl=1"

curl -x "$proxy_url"

This enables advanced session logic.

Debugging Requests

Monitor proxy requests/responses during development:

// Verbose debugging
proxy_url="http://username:[email protected]:8080/social?verbose=1"

curl -x "$proxy_url"

Multi-Threaded Scraping

BrightData supports concurrent requests from each proxy port.

So you can coordinate multiple cURL instances for faster data extraction without worrying about blocks.

Conclusion & Next Steps

Configuring cURL User Agents is necessary but challenging for effective large-scale web scraping. Mismanaging User Agents leads to 12% of blocks.

BrightData simplifies web data extraction with reliable rotating proxies designed specifically to defeat anti-scraping systems.

Key advantages:

  • Handles User Agents automatically
  • Unblockable proxy network
  • Easy integration with cURL
  • Advanced customization options

To get started with BrightData proxies, sign up for a free account and receive:

  • 5,000 requests/month
  • Dedicated account manager
  • Priority 7am-4pm PT support

With BrightData, you can focus on the data you want instead of fighting anti-scraping barriers.

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