Test Profiles

Test Profiles allow you to change the conditions that Calibre uses to test your site.

You can emulate popular devices (like iPhones, iPads and Nexus phones), as well as limit the bandwidth (latency, download and upload kb/s).

Emulated devices

Device emulation is achieved using Google Chrome’s device emulation—we go a few further steps to ensure that the experience is as close to a real device as possible.

Calibre currently emulates the same devices that you’ll find in the Chrome browser devtools emulation:

  • Motorola Moto G4
  • iPhone 5
  • iPhone 6
  • iPhone 6 Plus
  • iPhone 7
  • iPhone 8
  • Nexus 5X
  • Nexus 6P
  • Galaxy S5
  • iPad
  • iPad Pro

When Calibre emulates a device, the following occurs:

  • The device viewport is changed.
  • The User-Agent is set to that of the device.
  • The CPU will be slowed in line with the hardware of the device.

Emulated network connection speed

Calibre limits bandwidth by running through a high performance bandwidth limiting proxy server. Latency is added to each request/response cycle, and data is throttled as it passes through.

As of writing, the following bandwidth options are used:

  • No bandwidth throttling
  • Regular 2G (Latency: 300ms, Downstream: 31.25 KB/s, Upstream: 6.25 KB/s)
  • Good 2G (Latency: 150ms, Downstream: 56.25 KB/s, Upstream: 18.75 KB/s)
  • Regular 3G (Latency: 100ms, Downstream: 93.75 KB/s, Upstream: 31.25 KB/s)
  • Good 3G (Latency: 40ms, Downstream: 192.00 KB/s, Upstream: 93.75 KB/s)
  • Regular 4G (Latency: 20ms, Downstream: 512.00 KB/s, Upstream: 384.00 KB/s)
  • DSL (Latency: 5ms, Downstream: 256.00 KB/s, Upstream: 128.00 KB/s)
  • WiFi (Latency: 2ms, Downstream: 3.75 MB/s, Upstream: 1.88 MB/s)


Calibre applies the cookies that you supply to each corresponding browser session.

Heres just a few things that you could do with cookies:

  • Authenticate Calibre to your web app
  • Disable advertising to ease troubleshooting of dev specific regressions.
  • Test against an A/B test or staff-shipped feature.


Custom headers can be set via test profiles. This is useful for setting Authorisation headers for basic authentication or for triggering certain conditions for your pages.


Calibre’s agents are also able to test using an adblocker. If you’re curious to see how pages perform with or without ads this feature, create a new profile that blocks ads.

At the time of writing, Calibre’s adblocker is powered by uBlock.