Most tutorials that show you how to read YouTube comments stop at the
first page. Here is what actually happens when you try to read a thread
that has 40,000 of them.

The endpoint, and what it actually costs

Comments live behind commentThreads.list on the YouTube Data API v3:

GET https://www.googleapis.com/youtube/v3/commentThreads ?part=snippet,replies &videoId=VIDEO_ID &maxResults=100 &pageToken=NEXT_PAGE &key=YOUR_API_KEY

Two things bite people here.

It is quota-metered, not rate-limited. commentThreads.list costs 1 unit
per call against a default 10,000-unit daily quota. At maxResults=100 that
is 100 calls — and 100 calls is 1% of your day. A busy video with 40,000
comments needs 400 calls. You will hit the ceiling faster than you expect,
and the error is a plain 403 quotaExceeded, not a retryable 429.

maxResults is capped at 100 and the cap is silent. Ask for 500 and you
get 100 with no warning. Loop until a page returns fewer items than you asked
for, or you will spin forever on a video whose comment count is a multiple
of 100.

Pagination that actually terminates

The naive loop breaks in three places: the last page, a video with comments
disabled, and a video that is age-restricted.

import requests def read_thread(video_id: str, api_key: str): url = "https://www.googleapis.com/youtube/v3/commentThreads" token, seen = None, 0 while True: params = { "part": "snippet,replies", "videoId": video_id, "maxResults": 100, "key": api_key, } if token: params["pageToken"] = token resp = requests.get(url, params=params, timeout=15) # 403 covers both "comments disabled" and "quota exhausted".  # Read the reason, do not just retry.  if resp.status_code == 403: reason = resp.json()["error"]["errors"][0]["reason"] if reason == "commentsDisabled": return seen raise RuntimeError(f"quota or permission problem: {reason}") payload = resp.json() items = payload.get("items", []) seen += len(items) token = payload.get("nextPageToken") if not token: return seen

The nextPageToken is absent on the final page — that is your exit
condition. Do not compare against pageInfo.totalResults; it is an estimate
and it drifts on large threads.

Replies are a second request

commentThreads.list returns the top-level comment plus, by default, a
single reply. Getting the rest means calling comments.list with
parentId. On a thread with heavy back-and-forth this doubles or triples
your quota spend, and there is no way to know in advance how much.

If you only need the top-level conversation, do not request replies at all —
you get roughly 3x the coverage for the same quota.

When you do not want to write any of this

I built Apriocity because I kept writing this same
pagination loop for one-off research tasks. It does the paging, the quota
accounting and the reply expansion for you, and hands back CSV or JSON:

  • paste a video link, read the whole thread, search it by keyword
  • export the slice as CSV or JSON
  • batch mode: up to ten videos, one ZIP back

It uses the same public API described above, so what you see is exactly
what is publicly visible — nothing is stored on the server side.

The short version

  • commentThreads.list = 1 quota unit per call, maxResults capped at 100
  • nextPageToken missing = done; do not trust totalResults
  • 403 is overloaded: check the reason field before retrying
  • Replies cost extra calls — skip them unless you need them

If you are doing this once, the API is fine. If you are doing it weekly,
that loop is worth automating away.