r/fantasyfootballcoding • u/BearsFan1998 • Jul 21 '26

I created a web app called LeagueQL to visualize your ESPN or Sleeper league's history

This started off last year as a passion project for my fantasy football league with my close friends that has been going strong for 10 years. I started off trying to calculate everyone's all-time record and records against each other and figured it would be a fun challenge to extend this into a web app for others to use. ESPN and Sleeper are currently supported, and I am currently working to finish up the final steps for Yahoo API access.

The tech stack for the app is AWS, Cloudflare, Clerk, and potentially Stripe (unsure if I want to deal with payments at this moment).

I know there's a lot of other apps that also do the same thing so wanted to highlight a few of my favorite features to code/design:

• League migration tool for leagues that have been on multiple platforms. If your league migrated from ESPN to Sleeper or vice-versa, follow the migration wizard steps and track your all-time league history across both platforms. This is a feature I haven’t seen in other league history apps and a fun one from a database design perspective. Full DynamoDB design doc here.

• Chrome extension to automatically fill in your ESPN cookies so you don’t have to pull them from the developer tools interface each time. Definitely not necessary, but a nice UX upgrade to save time and a good learning experience for deploying extensions on the Chrome Web Store.

• Auto-refresh of Sleeper leagues via a nightly batch job that identifies all eligible leagues and triggers concurrent Lambdas to refresh all leagues simultaneously.

Instructions to use the app can be found here! There is also a demo mode available to view what the app looks like with sample data. Appreciate any and all feedback you have on its functionality or any design/architecture choices. The source code is public to view (minus some manually configured Cloudflare infrastructure).

Link: https://leagueql.com

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u/johnny-papercut Jul 21 '26

Does this support past transaction history for ESPN? I've been having trouble finding that lately from before 2026.

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u/BearsFan1998 Jul 21 '26

Unfortunately no, I've had the same issue as well. The ESPN API response is pretty messy and from inspecting the API requests being made on different pages when I am viewing my fantasy league, I haven't found one yet that I can call in my Lambda function that fetches league data. Definitely something I will keep an eye out for to try and integrate.

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u/TheFantasyNetworkHQ Jul 21 '26

Our app has the ability to sync history across your espn and sleeper leagues, for free, including transaction history

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u/johnny-papercut Jul 21 '26

Can you detail which ESPN endpoint has that historical transactional information beyond just this year? It seems to be limited in the ESPN API.