Understanding the Thread Limit
Every ProxyPorts proxy has a hard limit of 100 concurrent threads (simultaneous connections). This is the single most common cause of complaints about "0 kbit/s data transfer" or random connection drops — and it is almost always caused by exceeding this limit without realizing it.
What Is a "Thread"?
A thread is a single simultaneous connection lane through the proxy. Think of it like a highway with 100 lanes — each active connection occupies one lane. When all 100 lanes are in use, new connections are refused or existing ones are dropped.
Threads Are Not Devices
This is a critical distinction. The 100-thread limit is not the same as a 100-device limit. A single device — or even a single browser tab — can consume dozens of threads at once.
How Threads Get Used Up Fast
Web Browsers
A single browser tab loading a modern website can open 50+ simultaneous connections. This happens because:
- The page loads images, scripts, fonts, and stylesheets from multiple domains.
- Background processes like syncing, telemetry, and extension updates run constantly.
- Thumbnail previews and lazy-loaded content trigger additional requests.
If you have just 2-3 tabs open through the proxy, you can easily hit 100 threads.
Scraping and Automation Tools
Tools like Selenium, Puppeteer, and Scrapy are designed for aggressive parallel processing. They will:
- Open many connections simultaneously to speed up scraping.
- Instantly max out the 100-thread limit.
- Cause all connections to fail with timeout errors once the limit is exceeded.
How to Stay Within the Limit
- Limit concurrent browser tabs — Close tabs you are not actively using.
- Configure your scraper — Set the concurrency / max-connections parameter to 50 or below, leaving headroom for overhead connections.
- Use one proxy per task — If you need to run multiple heavy tasks (e.g., multiple scraping jobs), use separate proxies rather than routing everything through one.
- Monitor your usage — Use your dashboard to check active connections if you suspect you are hitting the limit.
What Happens When You Exceed 100 Threads?
New connections will be refused, and you may see:
- "0 kbit/s" data transfer in speed tests.
- Random page load failures.
- Timeout errors.
- Connections dropping mid-transfer.
The fix is always the same: reduce the number of simultaneous connections going through the proxy.