Stop Guessing. Start Winning.

Most drafters are working off gut feel, stale rankings sheets, and vibes. rosterOS puts a full analytics engine inside your Underdog Fantasy draft. It grades every player, tracks every stack, and tells you what your roster needs before you make the pick.

Coming Soon
Coming Soon

7-day free trial. $5/month after.

Payments processed securely by ExtensionPay and Stripe.

WHAT IT DOES

Every player on the board gets a letter grade, A+ to F, based on projected points, ADP delta, positional scarcity, and your current roster shape. The grade updates with every pick. Expand any player to see exactly what's driving the grade.

Grades That Mean Something

Heavy WR through four rounds? Light on early RB capital? The capital tracker shows your pick allocation by position against a target zone so you can see drift before it costs you. Roster construction is where Best Ball is won and lost. rosterOS makes it visible.

Build Shape Feedback in Real Time

Every pick, instantly simplified. RosterOS analyzes your roster in real time and surfaces exactly who to draft next, with the reasoning already done for you. No tab-switching, no second-guessing. Just your next pick, right when you need it.

Your Next Pick, Made Simple

The Stacks tab shows every correlation on your roster organized by team with High and Moderate strength ratings. It surfaces the best available players who would strengthen an existing stack and shows back-stack candidates.

Stacks You See Coming

Upload your Underdog draft history and every player shows your real exposure percentage and average draft capital from your actual drafts,. Filter by tournament type to see where you're thin or overweight in the specific field you're building for.

Your Portfolio, Right on the Board

Upload your own rankings CSV and rosterOS incorporates them into the grade model alongside ADP and projected points. Prefer a different value system? Bring it with you.

Your Rankings, Your Model

FAQ

  • Install the extension from the Chrome Web Store, open any Best Ball draft on Underdog Fantasy, and the overlay loads automatically. No configuration, no setup. Optionally upload your Underdog draft history CSV once from the popup to activate live portfolio tracking.

  • $5 per month. You get a 7-day free trial to start. After the trial, cancel anytime.

  • Cancel from the extension popup or from your account at extensionpay.com. No questions asked.

  • Yes. Upload your rankings CSV from the popup and rosterOS incorporates them into the grade model alongside ADP and projected points. You keep your edge and gain everything else on top of it.

  • No. Everything runs locally in your browser. Nothing is sent to a server during your draft. The overlay is fast because it has to be. You're on the clock.

  • Not yet — Superflex support is on the roadmap and coming soon. For now, RosterOS is optimized for 1-QB formats.

  • Export your draft history CSV from Underdog and upload it once from the extension popup. After that, every player on the board shows your real exposure percentage and average draft capital from your actual drafts. You can filter by tournament type to see where you're over or underweight in the specific field you're targeting.

  • QB Push flags QBs who are likely to fall to your next pick because no team between your current and next pick has motivation to take them. It's derived from the live board in real time.

  • RB Leverage flags handcuffs to early RBs already drafted by other teams. If that starter goes down, the team that drafted them collapses. You hold the backup and benefit twice. Both QB Push and RB Leverage come directly from the live board and don't exist in any standard ranking set.

  • No. rosterOS is an independent product and is not affiliated with, endorsed by, or sponsored by Underdog Fantasy.

  • Email info@rosterOS.com and we'll get back to you.

  • rosterOS runs entirely on your device and no data about you is ever sent to our servers. Your settings, uploaded draft history CSV, and a small local error log are stored in your browser's extension storage and stay there until you delete them. While you're in a draft, the extension reads the live page to power the overlay, but nothing from that session is recorded or transmitted. Once daily, the extension fetches public ADP and rankings data to stay fresh. The only external party that handles your personal data is ExtensionPay and Stripe for subscription management, which collect your email and payment details solely to process your subscription.

rosterOS Best Ball Overlay — Privacy Policy

Last updated: April 14, 2026

This Privacy Policy is available at https://rosteros.com/rosteros-best-ball-overlay#privacy-policy

Overview

rosterOS Best Ball Overlay is a Chrome browser extension that provides real-time draft analytics for Best Ball fantasy football drafts on Underdog Fantasy. We are committed to collecting only what is necessary to operate the extension.

Data We Collect and How It Is Used

User Settings

The extension stores your display preferences and onboarding status locally in your browser using Chrome's built-in storage API (chrome.storage.local). This data never leaves your device and is not transmitted to any server.

Uploaded CSV Data

You may optionally upload a CSV file containing your historical draft exposure data exported from Underdog Fantasy. This file is parsed and stored locally in your browser. It is never uploaded to or processed by any external server. You can delete it at any time from the extension popup.

Draft Session Data

While you are on an active Underdog Fantasy draft page, the extension reads live draft state from the page, including player names, positions, pick numbers, and your roster, to power the overlay. This data is processed locally in memory and is never transmitted or stored beyond the active session.

Error Logs

The extension maintains a local ring buffer of up to 50 error entries in chrome.storage.local to help diagnose issues if you report a bug. These logs are stored only on your device and are never automatically sent anywhere.

Subscription and Account

Payment and subscription management is handled by ExtensionPay (extensionpay.com), which uses Stripe as its payment processor. When you subscribe, ExtensionPay collects your email address and payment information. rosterOS does not store or have access to your payment details. Your email is used solely to manage your subscription. Please review ExtensionPay's privacy policy at extensionpay.com and Stripe's privacy policy at stripe.com/privacy for details on how they handle your data.

Data Sharing

We do not sell, rent, or share your personal data with any third parties, except as described above for payment processing via ExtensionPay and Stripe.

Data Retention

All locally stored data, including settings, CSV data, and error logs, remains on your device until you uninstall the extension or manually clear it from the popup. Subscription data is retained by ExtensionPay per their policy.

Your Rights

You can delete all locally stored extension data by uninstalling the extension or using the clear buttons in the extension popup. To cancel your subscription or delete your ExtensionPay account, visit extensionpay.com.

Changes to This Policy

If we make material changes to this policy, we will update the Last Updated date above. Continued use of the extension after changes are posted constitutes acceptance of the updated policy.

Disclaimer

rosterOS is an independent product and is not affiliated with, endorsed by, or sponsored by Underdog Fantasy.

Contact

For questions about this privacy policy, contact info@rosterOS.com.