Wiki › Project

2048 solver

Project · tool · 2026

2048 solver finds the best move in the game 2048, on the standard 4×4 board or a larger 5×5 one. It is a single file of C with no dependencies. Given a board, it prints the expected value of each of the four moves and picks the best.

code
./solve4 best "0 0 2 2 / 0 4 8 16 / 2 2 32 64 / 4 8 128 256"
Best move: up   (depth 6, 3117348 leaves, 242.4 ms)

How it works

  • Bitboards. Each cell is stored as a 4-bit exponent (1 means 2, 2 means 4, up to 15 for 32768). A 4×4 board fits in one 64-bit integer, and a 5×5 board in a 128-bit one.
  • Row tables. Every possible row is computed once at start-up: 65,536 rows for 4×4 and 1,048,576 for 5×5. Each entry stores the result of sliding left and right, the points scored, and a heuristic score. Vertical moves transpose the board, apply the row move and transpose back.
  • Expectimax search. The solver alternates two kinds of step:
    • your move: it takes the best of the four directions;
    • the game's move: it averages over every empty cell receiving a 2 (90% chance) or a 4 (10% chance).

Search depth adapts to how many different tiles are on the board. Unlikely branches (below 0.01%) are cut, a table caches positions already seen, and the four first moves are searched in parallel threads.

  • Heuristic. It rewards empty cells and neighbouring equal tiles, and penalises rows that don't rise or fall steadily. The weights come from a well-known open-source 2048 AI by nneonneo, generalised to rows of any length.

A built-in self-test checks the precomputed tables against a straightforward implementation. A JSON output mode makes it easy to drive from other programs, and an index.html provides a page for entering boards.

Limits

The largest tile is 32768, so two of them can't merge. The 5×5 board uses weights tuned for 4×4: they play well but aren't tuned for the larger board.

See also

In the knowledge graph

2048 solver and the 8 things it is linked to. Open any dot for its page, or explore it in the full graph.

C · skill · Built withCExpectimax search · technique · ImplementsExpectimax searchBitboard · technique · ImplementsBitboardGame tools and modding · theme · ThemesGame tools and mo…Algorithms and practice · theme · ThemesAlgorithms and pr…Open source on GitHub · person, role or place · ContextOpen sourceJSON · dataset or file format · File formatsJSON2048 · game or collection · Game2048 2048 solver
8 linked in the graph: 1 skill2 techniques2 themes1 person, role or place1 dataset or file format1 game or collection
When
2023202420252026
Oct 2026 · 1 commits

As data

Everything on this page is read from triples in the knowledge graph. These are the 20 it states about 2048 solver, and 5 more its ontology implies; the console runs SPARQL over the whole graph, here in your browser.

Download
@prefix id: <https://ask.chaipat.cc/id/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix cj: <https://ask.chaipat.cc/ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

id:Solver2048
    a cj:Project ;
    rdfs:label "2048 solver" ;
    cj:description "Expectimax solver for 4×4 and 5×5 2048 boards in a single C file." ;
    cj:context id:OpenSource ;
    cj:repository "https://github.com/AppleBoiy/2048-solver"^^xsd:anyURI ;
    cj:firstCommit "2026-10-28"^^xsd:date ;
    cj:lastCommit "2026-10-28"^^xsd:date ;
    cj:commitCount 1 ;
    cj:kind "tool" ;
    cj:theme id:ThemeGameTools , id:ThemeAlgorithms ;
    cj:uses id:C ;
    cj:tier 2 ;
    cj:implements id:Expectimax , id:Bitboard ;
    cj:handles id:JSONFormat ;
    cj:about id:Game2048 ;
    cj:article "https://ask.chaipat.cc/wiki/Solver2048"^^xsd:anyURI ;
    cj:activeIn id:Y2026 ;
    cj:activity _:b149 .