> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vertracloud.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Compare Periods in Web Analytics

> Turn on Compare to draw the previous period as a dashed line and see how visitors, requests, speed and errors changed since then.

Compare puts the period you are looking at next to the one right before it, so you can tell whether a number is good or bad for your site. It is available on every plan.

Same data through the API: [Application traffic](https://docs.vertracloud.app/api-reference/endpoint/apps/analytics/traffic.md). Send `compare=true`, and `compare_start` to choose where the compared period starts.

## How it works

Turn on **Compare** in the period bar. The previous period is the same length as the selected one, immediately before it:

| Selected | Compared with |
| - | - |
| Last 24 hours | The 24 hours before that |
| Last 7 days | The 7 days before that |
| A custom range | A range of the same length right before it |

You can also choose where the compared period starts. It always has the same length as the selected one:

| Compare with | Starts at |
| - | - |
| Previous period | Right before the selected one (the default) |
| Previous week | 7 days before the selected one starts |
| Custom | The date and time you pick |

A compared period that ends after the selected one starts is not accepted, because the two would overlap.

Two things change on screen:

* **Charts** draw the previous period as a dashed line over the current one, aligned by position in time.
* **Numbers** show the change, such as "+12%" for requests or a lower response time, next to the value.

## Reading the change

* More requests is not automatically good or bad: it depends on whether you launched something or a bot arrived.
* **Response time and error rate going up** is the part to act on. Check [Errors](https://docs.vertracloud.app/web-analytics/errors.md) and [Performance](https://docs.vertracloud.app/web-analytics/performance.md).
* A very small base exaggerates percentages: from 2 errors to 4 is "+100%". Look at the counts too.

## Limits

The compared period must also fit in the history of your plan; see [History and plans](https://docs.vertracloud.app/web-analytics/history-and-plans.md). Compare keeps working with filters: the same filters apply to both periods.

Next: [Sampling and delay](https://docs.vertracloud.app/web-analytics/sampling-and-delay.md).


This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.