How to track subscriber growth with the YouTube API

Two numbers, two APIs

The current total and the change over a window come from different places.

The total is on the Data API's channel resource:

curl -s 'https://www.googleapis.com/youtube/v3/channels?part=statistics&mine=true' \
  -H "Authorization: Bearer $ACCESS_TOKEN"

statistics.subscriberCount, as a string.

The change is on the Analytics API:

curl -s -G 'https://youtubeanalytics.googleapis.com/v2/reports' \
  -H "Authorization: Bearer $ACCESS_TOKEN" \
  --data-urlencode 'ids=channel==MINE' \
  --data-urlencode 'startDate=2026-10-01' \
  --data-urlencode 'endDate=2026-10-07' \
  --data-urlencode 'metrics=subscribersGained,subscribersLost' \
  --data-urlencode 'dimensions=day'

The total is rounded

This is the important one. Above a thousand subscribers YouTube rounds the count to three significant figures, publicly and in the Data API. 12,345 reads as 12,300.

The rounding gets coarser as the channel grows, so a large channel can gain hundreds of subscribers a day and report the same number for several days before stepping.

Consequences:

Do not build a growth series from the total. Polling subscriberCount daily and differencing it produces a staircase, with long flat runs and sudden jumps that correspond to the rounding boundary rather than to anything that happened.

Do not compute a daily gain from it. The difference between two rounded numbers has an error of up to the rounding increment, which on a large channel is larger than a normal day's gain.

The exact figures are in Analytics. Use them.

Gained is gross, not net

subscribersGained counts people who subscribed. subscribersLost counts people who left. YouTube reports them separately and does not net them.

A channel can gain two thousand and lose five hundred in the same week. A "new subscribers" figure that shows two thousand is correct and is not growth.

const net = gained - lost;

Net is the number that moves your total. Gross is the number that tells you whether your content is finding people, which is a different and also useful question. Report whichever you mean and label it.

Where subscriptions come from

Add the dimension and you get the surface:

dimensions=subscribedStatus,day

Or, more usefully:

dimensions=insightTrafficSourceType
metrics=subscribersGained

That tells you whether your subscribers came from search, from suggested videos, from a channel page or from an external link. The answer usually changes what you would do next far more than the total does.

The lag

Subscriber metrics settle like everything else in Analytics, over a day or two, and days are Pacific Time. A spike that looks like it happened on Tuesday in London may be Monday in the data.

A subscriber is not a viewer

Worth stating because the total is the number everybody optimises for. Subscribing costs one click and implies nothing about watching. A channel's subscriber count and its returning-viewer count can move in opposite directions for a long time.

If you want the number that predicts future views, it is watch time and returning viewers, not this one.

In the notch

Notch Metrics reports YouTube subscribers as the current total without a sparkline, because a chart of a rounded series draws steps that look like stalled growth. The change against the previous window comes from Analytics and is exact, so the arrow is right even where the total is rounded.

New subscribers is the gross gain in the window, and the page says gross rather than letting you assume net. Everything YouTube reports, or download Notch Metrics.