Cyclomatic Complexity Explorer

Add Control-Flow Construct

Lint Threshold

max-complexity rule 10

Cyclomatic Complexity

M = E − N + 2

✓ within threshold

E=0, N=1 → M = 0 − 1 + 2 = 1

Nodes (N)

Edges (E)

Decision points

Min. test paths

How it works

McCabe's Cyclomatic Complexity counts the independent execution paths through a function's control-flow graph (CFG) — every node is a basic block of statements, every edge is a possible jump between blocks:

M = E − N + 2P
E = edges, N = nodes, P = connected components (1 for a single function)

Equivalently, M = (number of decision points) + 1, where a decision point is any if, loop condition, or case branch. Real linters enforce this directly: ESLint's complexity rule, SonarQube's cognitive-complexity gate, and Android Lint's CyclomaticComplexity check all flag a function once M crosses a configurable threshold (commonly 10–15) — high M correlates with hard-to-test, bug-prone code because each extra path is a case your test suite can silently miss.

+ Statement — appends a straight-line block (no new path, N+1, E+1, M unchanged).
+ IF / ELSE — a 2-way branch that rejoins: adds one decision point, M+1.
+ LOOP — a back-edge to a loop header: also exactly one decision point, M+1.
+ SWITCH (3) — a 3-way branch: adds 2 decision points, M+2 (k cases add k−1).
Undo — removes the last construct and recomputes the graph from scratch.
max-complexity rule — mirrors a real linter config; the verdict badge turns amber near the limit and red once M exceeds it.

The 3D graph lays blocks out by depth (top → bottom) so you can watch branches fan out and rejoin exactly like a real CFG diagram in a static-analysis tool.

Basic block Decision node Entry

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