How to Add a Leaderboard to a Browser Game Without a Backend

To add a leaderboard to a browser game without a backend, use a hosting platform that stores and ranks scores for you, then have your game submit each player's best result and render the ranked list it gets back. On Fifth Door, the Platform SDK does this with shared records: you declare a scores collection, write one record per player, and read it already sorted. You never run a database or a server.

This guide covers how to design a leaderboard people care about, how it works on Fifth Door, and the prompt to give your coding agent or the create flow.

Why not just save scores in the browser?

Browser storage only holds one player's data on one device. A leaderboard needs every player's score in one place, ranked, and protected from one player overwriting another's entry. That is a server job.

There is a second reason on Fifth Door: published games run in a sandboxed frame where localStorage, sessionStorage, and cookies are not available. Code that saves there works in local testing and fails once the game is live. Scores and saves go through the SDK instead.

What makes a leaderboard worth checking?

A global all-time board where the top 10 is out of reach motivates almost nobody. Scope it so players can win something:

• Daily boards. Everyone starts at zero each day. This pairs well with daily puzzles; see how to make a daily puzzle game with AI.
• Friends boards. Only the people in the same room, so the competition is people you know.
• Per-mode boards. Separate boards for easy and hard, or for each level.
• Show the player's own rank, even when they are not in the top list.

Also decide what you rank: best score, fastest time, or a total. Keep that value as its own number.

How does a leaderboard work on Fifth Door?

The Fifth Door Platform SDK stores durable game data as records in collections your game declares. A leaderboard is one of those collections:

• One record per player per board. The platform stamps who owns each record, so players can only write their own entry.
• A declared sort order. You tell the platform which field ranks the board, and reads come back already ranked.
• Capped reads. A board read returns at most the top 100, which is plenty to render.
• Display names in the data. Records carry the owner's user ID, not a name, so store the name you want shown alongside the score.
• Filters and ranks. A board can filter by a declared field (such as day for a daily board), rank more than one way (best score and fastest time from the same results), and count a player's position.
• Live updates. A board scoped to a room can be watched, so scores appear as friends finish.

The collections are declared in a fifth-door.json file at the project root, and the SDK reference has the leaderboard recipe. If you build in your own editor, your agent can read those docs through the Fifth Door MCP server without signing in.

What should you tell your agent?

If you build with Claude Code, Cursor, or Codex, ask for the feature and point it at the docs:

"Add a daily leaderboard to this game using the Fifth Door Platform SDK. First read the SDK docs for collections and the leaderboard recipe. Each player has one record per day holding their display name and best score. Rank by best score, show the top 20, and show the player's own rank under the list. Do not use localStorage."

If you use the hosted create flow, describe it in plain language:

"Add a daily leaderboard. Each player's best score for today counts. Show the top 20 and my rank. It resets every day."

Then test it with two accounts or two devices so you can see more than one name on the board.

How do you publish a game with a leaderboard?

Publish the same way as any Fifth Door game. With the MCP server installed, ask your agent to publish; it uploads the bundle, including fifth-door.json, and returns a play URL. The collections you declared are set up at publish so the host can enforce them. Steps are in how to publish a vibe-coded game.

How do you make a leaderboard social?

A board gets more play when players can pull friends in:

• After a run, offer a share with the actual result ("Beat my 420 in Dropline"), not only the game title. The SDK's share call hands the player the right link.
• Offer a beat-my-score challenge link to one friend.
• For a group, invite friends into a room and show a room-scoped board. For rooms and invites, see how to make a multiplayer game with AI.

Common mistakes

• One global all-time board that nobody can climb
• Re-sorting the list in the game instead of rendering the platform's ranked order
• Storing only a user ID, so the board shows no names
• Saving scores to localStorage in a published game
• Never testing with a second player

FAQ

Can I add a leaderboard without writing a backend?

Yes. On Fifth Door, the Platform SDK stores and ranks scores as shared records, so the game only submits a score and renders the list.

Can I have a daily leaderboard?

Yes. Declare a day field, key each player's record by day, and read today's board with a filter. It starts fresh every day.

How many entries can a board show?

A board read returns at most the top 100, already ranked. Most games show 10 to 20 plus the player's own rank.

Can players cheat?

Each player can only write their own record. Your game still owns its scoring rules, so validate scores in the game logic before you submit them.

Do I need the SDK for a basic game?

No. A plain static game publishes and runs without it. Add the SDK when you want leaderboards, saves, rooms, or daily puzzles.

Add a board to your next game

Pick one scoped board (daily or friends), ask your agent or Fifth Door create to add it, test it with a second player, and share a result link. Then see how other games use boards on Discover.