An RSS reader sends periodic requests to get the latest feed. This includes a User-Agent field, identifying which fetcher is running:

Feedbin feed-id:1242010 - 38 subscribers

This fetcher is nicely passing along statistics, saying how many readers it represents.

I took one day of logs, with 5,962 requests for my RSS feed:

$ sudo grep '"GET /news.rss ' \
    /var/log/nginx/access.log.1 \
  | awk -F'"' '{print $6}' \
  | wc -l
5962

There were 162 unique User-Agents:

$ sudo grep '"GET /news.rss ' \
    /var/log/nginx/access.log.1 \
  | awk -F'"' '{print $6}' \
  | sort \
  | uniq \
  | wc -l
162

Of the 5,962 requests, 932 (16%) gave stats:

$ sudo grep '"GET /news.rss ' \
    /var/log/nginx/access.log.1 \
  | awk -F'"' '{print $6}' \
  | grep 'subscriber\|reader' \
  | wc -l
932  

They sent 21 distinct User-Agents:

$ sudo grep '"GET /news.rss ' \
    /var/log/nginx/access.log.1 \
  | awk -F'"' '{print $6}' \
  | grep 'subscriber\|reader' \
  | sort \
  | uniq \
  | wc -l
21

Some sent multiple requests with different numbers of subscribers:

Feedbin feed-id:1242010 - 38 subscribers
Feedbin feed-id:372940 - 11 subscribers
Feedbin feed-id:382 - 1 subscribers

I suspect this comes from people using old URLs that then get redirected to my current URL. For example, now it's https://www.jefftk.com/news.rss, but it used to be http://www.jefftk.com/news.rss, and even longer ago it was an sccs.swarthmore.edu address. Summing subscriber counts, I see:

• Feedly: 573
• inoreader.com: 87
• NewsBlur: 62
• Feedbin: 50
• theoldreader.com: 34
• Dreamwidth Studios: 7
• BazQux: 5
• Bloglovin: 2
• Feed Wrangler: 2
• pine.blog: 1

While this only tells us about users who are subscribed to my blog, it seems like Feedly is the biggest player here by a lot.

Different services fetched at different intervals. Taking the shortest interval for each distinct User-Agent:

• Feedly: 7min
• Feedbin: 15min
• Bloglovin: 30min
• Dreamwidth Studios: 30min
• Feed Wrangler: 30min
• NewsBlur: 30min
• BazQux: 40min
• inoreader.com: 1hr
• theoldreader.com: 2hr
• pine.blog: 24hr

Looking through the requests that don't list subscribers, several do seem to be services. I'll try reaching out to them to see if they're interested in adding subscriber counts to their User-Agents.