Stabilizer Simulator
A statevector needs 2ⁿ amplitudes, which is why the main simulator stops at 16 qubits. A circuit made only of Clifford gates never needs them: its state is pinned down by n Pauli operators, and each gate just rewrites that list (the Gottesman–Knill theorem; the tableau algorithm here is Aaronson & Gottesman, 2004). So this page runs up to 4,096 qubits in your browser, exactly — and refuses a T gate, because no list of Paulis can follow one.
H then a chain of CNOTs. One bit of entanglement across every cut, however long the chain.
What this is not
Not a faster general simulator. Clifford circuits are exactly the ones a classical computer can follow efficiently; add enough T gates and the cost climbs back to exponential. What a tableau is for is everything in error correction — syndrome circuits, decoders and thresholds are all Clifford — and large-scale entanglement dynamics such as the measurement-induced transition. To check a code rather than a circuit, use the Stabilizer Code Explorer.
The engine is cross-checked against this site’s statevector simulator on random circuits up to 6 qubits: every generator it reports must stabilize the actual amplitudes, sign included.