The API /tag stats are notably different from the site totals

Question

Why this discrepancy?

--Sep 10 2015 11:26:09 GMT+0530 (IST)--

• At that time, the API shows 42010 tags.

• But the same thing computed on the Stack Overflow tags page is 44496.

Is it because of caching?

Answer 1

There seem to be 2 or 3 effects, the biggest is that the Tags page also shows Synonyms.

There may also be a small cache effect, but there seems to be another discrepancy as well, possibly an error/bug.

---

You can see that the Tags page also shows Synonyms by:

1. Go to the Tags page.
2. Enter userscr in the Type to find tags: box.
3. You will see something like:
   
4. Then use the Synonyms pages to see that userscript is a synonym of userscripts, not a real tag.
5. The API call reflects this.

---

Combining the API's /tags route and the /tags/synonyms route, I currently get:

42020 + 2442 = 44462

If you count up all the tags on the Tags page(s), I currently get:

     4 columns
*    9 rows
* 1236 pages
+   10 on the last page (page 1237)
-----------------------------------
44,506

Which still gives a discrepancy of 44!

This is too big to be explained by caching. The Tags page seems almost real-time and the API count is updating at least once an hour.

The latest SEDE data is currently from Sep 6 at 6:11 (about 4 days ago) and SEDE shows that there were 44,377 tags + active synonyms at that time.

This suggests a growth rate of about 32 tags per day, or about 1.3 tags per hour -- which matches the observed increase in the API results.

This final discrepancy (44) is something else; quite possibly a bug.

---

Cross checking the Tag Synonyms page(s), set to the active tab gives:

    24 pages
*  100 Synonyms per page
+   42 on the last page (page 25)
-----------------------------------
  2442

Which agrees with the API result.