<!-- https://developers.silktide.com/v1/analytics/audience/get-duration-over-time | Analytics / Audience -->

# Get how long visits lasted, step by step over a period

`GET /v1/results/analytics/duration-over-time`

Returns how long the average visit lasted in each step of a period, and across the whole of it, for an analytics view or a website.

Duration is engaged time: the seconds the visitor was actively using the pages of a visit, not how long a tab stayed open. Some visits record more engaged time than one person could have spent in them, such as colleagues behind one office network who look like a single visitor, or a computer that slept with the page open. Those are left out of the average and counted in `unmeasuredSessions`, with their page views in `unmeasuredPageViews`, so you can tell how much of the traffic the average does not cover. They are still visits, in `totalSessions`.

`total` weights each step by its measured visits, so do not average the steps to get it.

The old documentation named the average `observedDuration`. It is `engagedDuration`.

Send a `period`. With the default, `all`, this answers with an error. How long each step is, and how to choose it, is under [Over time](https://developers.silktide.com/v1/analytics/audience.md). A `filters[url]` filter matches the page each visit started on. Traffic collected at the Basic consent level records no visits, so it is not counted here.

## Request

### Query parameters

- `view` (string, optional, matches `^(all|[1-9]\d*)$`): The analytics view to read: its id, the number after `/analytics/` in its address in Silktide, or `all` for all of the account's analytics. Send this or `websiteId`.
- `websiteId` (integer, optional, at least 1): Instead of `view`, a website whose analytics to read. The website must have Analytics set up.
- `sectionId` (integer, optional): With `websiteId`, a section of the website. Defaults to `0`, the whole website.
- `period` (string, optional): The date range. Defaults to `all`. The spaced forms (`-7 days`, `month to date`) are older names that keep working. `custom` needs `from` and `to`. One of: `all`, `today`, `last-7-days`, `last-30-days`, `last-90-days`, `month-to-date`, `last-month`, `year-to-date`, `last-12-months`, `custom`, `-7 days`, `-30 days`, `-90 days`, `-1 month`, `month to date`, `year to date`, `-12 months`.
- `from` (string, optional): With `period=custom`, the first day, such as `2026-10-01`.
- `to` (string, optional): With `period=custom`, the last day.
- `timezone` (string, optional): The IANA time zone days are read in, such as `America/New_York`. Defaults to `UTC`.
- `filters` (map of strings, optional): Only visits matching every filter, keyed by what is filtered: `filters[url]=contains:/blog`. Each value is `{operator}:{value}`, with operator `is`, `not`, `contains`, `starts`, `gt` or `lt`. Keys include `url`, `hostName`, `entryUrl`, `exitUrl`, `event`, `outgoingUrl`, `referrer`, `source`, `medium`, `campaign`, `content`, `term`, `countryCode`, `regionCode`, `language`, `deviceType` (`desktop`, `tablet` or `mobile`), `operatingSystem` and `browser`.
- `interval` (string, optional): With `period=custom`, the length of each step: an hour, a day, a week starting on Monday, a month or a year. Ignored with any other period. Left out, steps are hours for a single day, months for exactly twelve months, and days otherwise. One of: `PT1H`, `P1D`, `P7D`, `P1M`, `P1Y`.
- `previousPeriod` (string, optional): `1` to add the figures of the period before, the same length and ending where this one starts, as `previous…` fields. Left out or `0`, none. Needs a `period` with a start: with `all`, nothing is added. One of: `0`, `1`.

## Response

Status `200`.

- `result` (object, required): The answer.
  - `series` (list of objects, required): One step per hour, day, week or month of the period, oldest first. A step with no visits reads `0` throughout.
    - `time` (string, required, matches `^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}$`): When the step starts, as `YYYY-MM-DD HH:MM:SS` in the request's `timezone`.
    - `engagedDuration` (integer, required): The average seconds a visit in the step was actively used, over its measured visits, rounded to a whole second. `0` when it had none.
    - `totalSessions` (integer, required): Every visit in the step.
    - `measuredSessions` (integer, required): The visits the average is over.
    - `unmeasuredSessions` (integer, required): Visits left out of the average because their engaged time could not be one person's.
    - `sessionPageViews` (integer, required): Page views in all of the step's visits.
    - `unmeasuredPageViews` (integer, required): Page views in the visits left out of the average.
    - `previousEngagedDuration` (integer, optional, can be null): The average engaged seconds in the matching step of the period before. Only with `previousPeriod=1`. Null when that period has no step in the same place, which weekly and monthly steps can cause.
    - `previousTotalSessions` (integer, optional, can be null): Every visit in the matching step of the period before. Only with `previousPeriod=1`. Null when that period has no step in the same place, which weekly and monthly steps can cause.
    - `previousMeasuredSessions` (integer, optional, can be null): Measured visits in the matching step of the period before. Only with `previousPeriod=1`. Null when that period has no step in the same place, which weekly and monthly steps can cause.
    - `previousUnmeasuredSessions` (integer, optional, can be null): Visits left out in the matching step of the period before. Only with `previousPeriod=1`. Null when that period has no step in the same place, which weekly and monthly steps can cause.
    - `previousSessionPageViews` (integer, optional, can be null): Page views in visits in the matching step of the period before. Only with `previousPeriod=1`. Null when that period has no step in the same place, which weekly and monthly steps can cause.
    - `previousUnmeasuredPageViews` (integer, optional, can be null): Page views in visits left out in the matching step of the period before. Only with `previousPeriod=1`. Null when that period has no step in the same place, which weekly and monthly steps can cause.
  - `total` (number, required): The average engaged seconds of a visit across the whole period, not rounded: each step's average weighted by its measured visits.
  - `range` (object, required): The dates the series covers.
    - `start` (string, required, matches `^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}$`): When the first step starts, as `YYYY-MM-DD HH:MM:SS` in the request's `timezone`.
    - `end` (string, required, matches `^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}$`): When the range ends, as `YYYY-MM-DD HH:MM:SS`: midnight after its last day, so the range runs up to but not including it.
  - `previousTotal` (number, optional): The same average across the period before. Only with `previousPeriod=1`.
- `selector` (string, required): The query that answered, as its path: `/v1/results/scores`.
- `duration` (number, required): Seconds Silktide took to answer.

## Errors

| Status | Type | When |
| --- | --- | --- |
| 404 | `ModelNotFound` | No view or website with that id exists in the account, or the API key's user cannot see it. |
| 403 | `AccessDenied` | The API key's user cannot read that analytics view. |
| 200 | `ModelNotFound` | The website has no Analytics set up. The body is an error despite the status. |
| 200 | `InvalidRequest` | Neither `view` nor `websiteId` was sent. The error's own `status` is `400` and `properties.field` is `view`. The body is an error despite the status. |
| 200 | `InvalidArgument` | A filter names a key or operator Analytics does not know. The body is an error despite the status. |
| 200 | `Error` | `period` is `all` or left out, which means `all`. Over-time queries need a period with a start. The body is an error despite the status. |
| 200 | `InvalidArgument` | `period` is not one of its values, or is `custom` without both `from` and `to`. The body is an error despite the status. |
| 200 | `Unspecified` | `interval` is not one of its values. The body is an error despite the status. |
| 401 | `NotLoggedIn` | No API key was sent, or it is not a key for this region. |
| 429 | `TooManyRequests` | Too many requests to this path in five seconds. Retry after the number of seconds in the `Retry-After` header, which `properties.retryAfter` repeats. |
| 503 | - | Silktide is busy. Retry after the number of seconds in the `Retry-After` header. |

## Access

- Permission: View analytics view (View all analytics for `view=all`)
- Plan feature: none
- Edition: Silktide 4 and Silktide 5
- Cost: free
- Stability: stable, since 1.0.0

## Example: Average visit length each day

```bash
curl "https://api.eu.silktide.com/v1/results/analytics/duration-over-time?view=all&period=custom&from=2026-10-01&to=2026-10-03" \
  -H "Authorization: silktide token=$SILKTIDE_API_KEY"
```

Response:

```json
{
  "result": {
    "series": [
      {
        "time": "2026-10-01 00:00:00",
        "engagedDuration": 54,
        "totalSessions": 244,
        "measuredSessions": 243,
        "unmeasuredSessions": 1,
        "sessionPageViews": 546,
        "unmeasuredPageViews": 12
      },
      {
        "time": "2026-10-02 00:00:00",
        "engagedDuration": 58,
        "totalSessions": 254,
        "measuredSessions": 254,
        "unmeasuredSessions": 0,
        "sessionPageViews": 586,
        "unmeasuredPageViews": 0
      },
      {
        "time": "2026-10-03 00:00:00",
        "engagedDuration": 62,
        "totalSessions": 236,
        "measuredSessions": 236,
        "unmeasuredSessions": 0,
        "sessionPageViews": 670,
        "unmeasuredPageViews": 0
      }
    ],
    "total": 57.96180081855389,
    "range": {
      "start": "2026-10-01 00:00:00",
      "end": "2026-10-04 00:00:00"
    }
  },
  "selector": "/v1/results/analytics/duration-over-time",
  "duration": 0.011
}
```