Real-Time Draft Guidance, Right Where You Draft

The rosterOS Chrome browser extension adds a live intelligence layer to your Underdog and DraftKings draft rooms: grading every pick against your roster, the market, and tournament upside in real time, with stack leverage and exposure tracking built in. It is free to use, and your draft data stays private with on-device processing.

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WHAT IT DOES

Grades Built For Your Draft

Stop guessing on the clock. rosterOS grades every available player in real time so you always know whether you are looking at a value, a reach, or a perfect fit for where your roster is headed. It works the same way in Underdog and DraftKings best ball draft rooms.

Every grade is built from ADP context, your current positional capital, roster construction fit, position scarcity, and tournament upside from full-season simulations: spike-week rates, playoff-week ceilings, and weekly floor impact. The result is a signal that is specific to your draft, not just a generic ranking.

Grade factor pills break down exactly why a player scored the way they did: Value or Reach, Fits Build or Off Build, Won't Last or Can Wait, and stack correlation signals, with an Anti-Stack flag when a pick works against what you have already built. Plain-language tags like "Playoff spiker," "Heats up late," and "Raises your weekly floor" tell you what a pick does for the weeks that decide tournaments. You get the reasoning, not just the number.



Pick Timing That Reads The Room

The hardest call in a draft is not who is best. It is whether to take a position now or get the value back later. rosterOS prices your future picks against live ADP and tells you directly: "Take now" when a position's window is closing, "Can wait" when the value survives to your next turn.

Quarterback rooms get the same treatment. The overlay knows when it is time for your QB2, when your QB room is already set, and when a third quarterback adds real weeks instead of just filling a roster spot. On DraftKings 20-round boards it plans for the deeper format automatically.

Timing recommendations recalculate on every pick the room makes, so the advice tracks your actual draft, not a preseason script.



Draft Capital Tracker

One of the most common ways best ball drafts go sideways is quiet over-commitment to a position before you realize it happened. rosterOS tracks your positional capital in real time so you can see the imbalance before it becomes a problem.

Capital by Position gives you a live snapshot of where your picks are going, round by round. Target Roster shows a per-position pace that adjusts to your picks and the live board, with each position marked on pace, behind, or set, and the reason spelled out in plain language. Combine that with the Build Advisor and you have everything you need to stay intentional about your roster shape from the first pick to the last.



Build Advisor

Best ball is about building a roster that works as a system, not just collecting good players. rosterOS tracks your emerging build archetype as the draft unfolds and shows you whether your roster is taking the shape you intended.

See your positional construction, your ADP value per pick, your rank value per pick, and how your draft compares to your intended strategy at every stage. When your build starts drifting, you will know early enough to adjust rather than react.



Stack And Correlation Tools

Stacking is one of the highest-leverage decisions in best ball fantasy football, and rosterOS surfaces every opportunity before the window closes. The Stacks tab shows your current stacks by team, available QB stack targets that fit your roster, and back-stack candidates so you can take the QB while his pass catchers are still on the board.

Player badges flag correlation opportunities directly on the board so you never have to cross-reference manually. The STK badge marks players that complete a same-team stack with your roster. The QB badge signals that a skill player's quarterback is still available, keeping a player-now, QB-later path open. The LEV badge highlights handcuff leverage behind an early running back drafted by another team in your room. Hedge warnings tell you when a pick mostly bets against a player you already own.

Playoff Stacking and Week 17 Boost controls let you tune how much weight the overlay puts on late-season scheduling and matchup advantages. Build for the weeks that decide championships, not just average production across the full season.



Live Portfolio Sync

Knowing your exposure while you draft is one of the biggest edges in a high-volume best ball season. rosterOS connects to your Underdog or DraftKings account and syncs your full draft history in one click, no CSV export required.

Your portfolio data loads live into the overlay so you can see pair tendencies, player exposure, and combo patterns while you are on the clock. Combo Ownership shows how your current pairings compare to the field so you can find differentiation when you want it or lean into chalk when the value is right.

Everything is processed locally in your browser. Your session data and portfolio history never leave your device and are never stored on any server. Your Underdog session token lives only in session storage and is deleted automatically when you close your browser. For drafters who prefer manual control, CSV upload is also supported as a fallback.



Custom Rankings

Draft to your process, not someone else's. rosterOS lets you upload your own player rankings and use them as the basis for grading throughout your draft. Your rankings adjust value signals, grade calculations, and positional context across the entire overlay.

Upload a simple CSV with player name and rank columns, for Underdog, DraftKings, or both. rosterOS reports exactly which names matched each site's board, so nothing silently misses, and when your rank and the model disagree on a player, the board shows both numbers side by side. Players not in your file keep rosterOS ranks.

Swap in a new file anytime without losing your session or your settings. Pair custom rankings with Rank Trust tuning in Draft Preferences to control how heavily your rankings influence the grades versus ADP-based signals.

FAQ

How does it work?

Install the extension, join a best ball draft on Underdog or DraftKings, and the overlay appears in the draft room automatically. It reads the live board and grades every available player in real time against ADP, your roster construction, position scarcity, and tournament upside.

As picks happen, grades, badges, stack signals, and timing recommendations update instantly. Everything runs locally in your browser.

Will it slow down my draft?

No. All processing happens locally on your device, with the heavy math running in a background thread, so the draft page stays responsive. There are no server round trips during your draft, and the overlay never modifies or interferes with the draft site itself.

I already have a rankings set I trust. Can I use it?

Yes. Upload a CSV with Name and Rank columns in the popup, for Underdog, DraftKings, or both. rosterOS reports exactly which names matched each site's board so nothing silently misses, and players not in your file keep rosterOS ranks.

Your ranks drive the value signals, and the Rank Trust setting controls how heavily they weigh against ADP. When your rank and the model disagree on a player, the board shows both numbers so you can make the call.

What do the badges mean?

STK marks a pick that completes a same-team stack with your roster. QB flags a skill player whose quarterback is still on the board, keeping a stack path open. LEV highlights handcuff leverage behind an early running back drafted by another team in your room. BYE warns when a pick shares a bye week with players you already roster at that position.

Grade pills explain each grade in plain language: Value or Reach, Fits Build or Off Build, Won't Last or Can Wait, plus stack and hedge signals. Expand any player row for the full reasoning.

What is portfolio tracking and how do I set it up?

Portfolio tracking shows your exposure while you draft: player percentages, pair tendencies, and how your combos compare to the field. It is one click to set up. While signed in to Underdog or DraftKings, open the popup and hit Sync; rosterOS uses your existing login session to pull your draft history. No password is needed and nothing leaves your browser.

Prefer manual control? Upload an exposure CSV instead. Re-sync anytime after you finish new drafts.

Does rosterOS support Superflex leagues?

Not currently. rosterOS is built for Underdog and DraftKings best ball formats, which start one quarterback. The grading engine's quarterback logic is tuned for those formats, so superflex drafts are not supported today.

Is rosterOS affiliated with Underdog Fantasy or DraftKings?

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

Does rosterOS use my data?

Your data stays on your device. Draft data, synced portfolios, uploaded CSVs, and custom rankings are processed and stored locally in your browser. Your Underdog session token lives only in session storage and is deleted automatically when you close your browser. There are no analytics or trackers, and nothing is transmitted to rosterOS servers.

The full details are in our Privacy Policy.

How do I get support?

Email us at info@rosterOS.com. If the overlay is not appearing, the quick fixes are refreshing the draft tab and confirming Overlay Enabled is on in the popup.

Privacy Policy

Effective date: July 9, 2026

rosterOS is built to help you draft better while keeping control of your data in your hands. This Privacy Policy explains what data we process, how we use it, and what choices you have.

1) Scope

This policy applies to:

  • rosterOS.com
  • The rosterOS Chrome extension
  • The rosterOS visualizer app (app.rosteros.com)

2) What We Process

Draft CSV data (local processing)

When you upload draft CSV files, rosterOS processes them locally in your browser. Draft CSV contents are not uploaded to rosterOS servers. Uploaded CSV files may include player names, contest entry-fee or prize fields, and draft metadata.

Underdog session token and portfolio sync

To power the Underdog portfolio sync feature, the extension intercepts your active Underdog session token (a Bearer JWT) from network requests your browser makes to Underdog's API. This token is:

  • Held in session-scoped extension storage only — it is never written to persistent storage and is deleted automatically when you close your browser
  • Used solely to fetch your own Underdog draft history on your behalf
  • Never transmitted to rosterOS servers or any third party
  • Accessible only by the rosterOS extension, not by web pages
  • Removable at any time with the Clear control in the extension popup

Your Underdog portfolio data retrieved using this token (draft picks, entry IDs, player selections) is stored locally on your device and processed entirely within the extension.

DraftKings portfolio sync and draft rooms

DraftKings features use your existing DraftKings login session. The extension does not capture, store, or transmit your DraftKings password, session cookies, or payment details. To power the live overlay and the optional portfolio sync, the extension observes identifiers from your own requests to DraftKings (such as the contest key and draft group ID of a draft room you open) and calls DraftKings' own APIs from your browser, as you. Your DraftKings portfolio and draft-room data are stored locally on your device and processed entirely within the extension.

Custom rankings (local processing)

If you upload custom rankings, they are parsed and stored locally in extension storage. You can maintain separate rankings for Underdog and DraftKings; both stay on your device.

Local extension/app storage

The extension and app may store settings and computed results locally on your device so features work across sessions. Examples include uploaded CSV-derived portfolio stats, synced Underdog or DraftKings portfolio data, UI preferences, custom rankings, and a small local error log used for troubleshooting. The error log never leaves your device.

Live draft-page context (extension)

The extension reads in-page draft state needed to provide real-time analytics in supported Underdog and DraftKings draft rooms. On Underdog, to intercept network requests before they are sent, the extension injects a script into the page's JavaScript environment; this script observes only requests to Underdog's API. On DraftKings, the extension reads live draft-room state via DraftKings' own draft API using your existing session. In both cases the extension does not read payment details, passwords, or any data unrelated to the draft session.

Technical website/hosting data (website only)

On rosterOS.com, basic technical logs (such as IP address, browser type, request timestamps, and error logs) may be processed by infrastructure providers for security, uptime, and abuse prevention.

3) How We Use Data

We use processed data to:

  • Power draft analytics and portfolio insights
  • Sync your Underdog or DraftKings draft portfolio on your behalf
  • Save user preferences and improve product reliability
  • Maintain service security and performance

We do not sell personal data.

We do not use analytics or tracking in the extension, and we do not transmit your session token, portfolio data, custom rankings, or uploaded CSV contents to rosterOS servers or any third party.

4) External Services and Data Sources

The extension downloads public data files (rankings, ADP, and schedule data) from the rosterOS data repository hosted on GitHub. These are read-only requests for public files and contain no information about you beyond standard request metadata. If you click "Send to Visualizer," your locally computed draft export is written into the visualizer page (app.rosteros.com) within your own browser — nothing is sent otherwise. Infrastructure providers may process technical request metadata under their own privacy terms.

5) Cookies and Tracking

rosterOS does not use advertising trackers in the extension experience. If essential cookies or similar technologies are used on the website for core functionality, they are limited to necessary operation and security.

6) Data Retention and Deletion

Locally processed draft CSV data, custom rankings, and synced portfolio data remain under your control on your device unless you delete them. Your Underdog session token is deleted automatically when you close your browser, when it expires, or when you press Clear. You can clear extension/app local data through the popup's Clear controls, browser extension controls, or by uninstalling the extension, which removes all locally stored data. Infrastructure logs are retained only as long as needed for operations, security, and legal compliance.

7) Your Choices

You can:

  • Choose whether to upload draft CSV files or custom rankings
  • Choose whether to use the Underdog or DraftKings portfolio sync
  • Remove local data, synced portfolios, and the session token at any time
  • Stop processing by uninstalling the extension or discontinuing use

8) Changes To This Policy

We may update this policy from time to time. When we do, we will update the effective date at the top of this page.

9) Contact

If you have privacy questions, contact us at: info@rosterOS.com