Digital Impact Factor

A quality index for educational blogs/podcasts


Longevity and sustainability are increasingly challenging for those who teach on open-access blogs and podcasts in the Free Open Access Medical education (FOAM) world. Financial and opportunity costs, higher learners expectations, and lack of academic credibility are a few of the reasons. The Social Media Index was originally created in 2016 to help bloggers and podcasters receive feedback on their impact and standing in the FOAM community. Since the Alexa Traffic Rank metric retired in 2022, we decided to overhaul the Social Media Index to include industry-standard webometric tools and feedback from the educator community.

We created the “Digital Impact Factor” quality index. We use this term because, similar to journals, many educational blogs and podcasts could be considered scholarly publications. Thus our new webometric tool partly incorporates weighted backlink counts to the website, similar to how the journal impact factor incorporates citation counts.

How is the Digital Impact Factor Helpful?

Although our primary goal is to help bloggers and educators achieve greater visibility, credibility, and academic legitimacy, this quality index list benefits many groups:

  1. University Promotion and Tenure Committees: The Digital Impact Factor provides those unfamiliar with the FOAM world with some objective measure of impact for an academic blogger/podcaster.
  2. Educators and Learners: This list provides a starting point in identifying high-quality educational content online.
  3. Education Researchers: Research about the blogging and podcasting modality requires a defined sample.
  4. Clinical Researchers: Researchers can optimize the dissemination of their research by sharing on high-impact sites.
  5. Freelancer Authors: Educators, who wish to start blogging or podcasting, can identify quality sites to contribute guest content rather than starting a new site on their own.
  6. Funders: Funding organizations and donors may wish to identify and help finance impactful and high-quality FOAM sites.


Lin M, Phipps M, Chan TM, Thoma B, Nash CJ, Yilmaz Y, Chen D, He S, Gisondi MA. Digital Impact Factor: A Quality Index for Educational Blogs and Podcasts in Emergency Medicine and Critical Care. Ann Emerg Med. 2023 Mar 24:S0196-0644(23)00119-1. doi: 10.1016/j.annemergmed.2023.02.011. Epub ahead of print. PMID: 36967275 [download open-access PDF article]


The Digital Impact Factor incorporates website authority (maximum score of 5) and social media followership (maximum score of 5).

  • Authority: The industry standard for website authority, Ahrefs Domain Rating, is based on weighted backlink counts such that inbound links to your site from a higher quality site will count more than spam sites. Domain Rating’s methodology preclude it from distinguishing backlinks to a parent or child site. So blogs and podcasts hosted on subdomains or subdirectories were excluded from the list. One exception we decided to leave on the list were FOAM sites on departmental-level parent websites, which we assumed had relatively few backlinks and traffic.
  • Social Media Followership: Unlike the Social Media Index where we included only Twitter and Facebook followers, we started with the top 10 most popular social media platforms. We excluded 2 (SnapChat and WhatsApp) because they were private messaging apps. Each platform, however, was weighted adjusted based on the total number of FOAM site followers on that platform divided by the overall total number of FOAM site followers summed over all 8 platforms. This proportional adjustment corrects for social media platforms rising and falling in popularity for future calculations (ahem, Twitter).
    • Instagram example: The adjustment factor was 198,687 (total Instagram followers for all FOAM sites) divided by 1,828,557 (total number of FOAM followers across all 8 platforms), or 10.9%.

Digital Impact Factor Formula for blogs and podcasts

Abbreviations and terms

  • DIF: Digital Impact Factor
  • Site: Blog or podcast website
  • DR: Ahrefs Domain Rating
  • P: Social media platform (Twitter, Facebook, Instagram, LinkedIn, Pinterest, Reddit, TikTok, Youtube/Vimeo)
  • Pall: Follower count for all sites on 1 social media platform
  • Total followers: Follower count for all sites on all 8 platforms
  • Psites: Follower count for the site on 1 social media platform
  • Pmax: Follower count for highest followership site on 1 social media platform

2023 Digital Impact Factor Scores for Emergency Medicine Blogs/Podcasts

There were fewer active blogs and podcasts in EM (79) than last year (87) with 5 new sites added and 13 retired. The social media followership counts were calculated during November 22-27, 2023, and the Domain Ranks were recorded on December 7, 2023. The 79 indexed sites can be filtered by format type (blog or podcast) in the drop-down menu. It can also be sorted by rank, site name, DIF score, relative Domain Rank, and relative social media reach by clicking on the header. Clicking again will toggle into an inverse order. You need to scroll to view the entire list.

May take a few seconds to load. If the view is still empty, try to filter by blog or podcast to try to jump start the loading.

* We categorized sites as “blogs” if they contained reverse chronological text-based and graphics-based posts. We categorized sites as “podcasts” if they contained primarily audio recordings. If they had both, we categorized them as “blogs”.


We would love to hear positive and negative feedback. We hope to iterate improvements over time with your input. This is not a perfect bibliometric tool for educational blogs and podcasts, but it’s the best we can derive thus far. Email us at [email protected].

Michelle Lin, MD
ALiEM Founder and CEO
Professor and Digital Innovation Lab Director
Department of Emergency Medicine
University of California, San Francisco
Michelle Lin, MD


Professor of Emerg Med at UCSF-Zuckerberg SF General. ALiEM Founder @aliemteam #PostitPearls at Bio:
Michelle Lin, MD
Mina Phipps

Mina Phipps

ALiEM Social Media Index Data Archivist;
Undergraduate student
Stanford University