AlgorithmsSortingRuns in your browserReviewed October 1, 2026

Merge Sort Visualizer

Split the list in halves, sort each half, then merge them back in order. Interactive step-by-step animation with JavaScript code, complexity and front-end use cases.

Localprivate by defaultFastno sign-up path

SortingTime: O(n log n)Space: O(n)

Numbers (2 to 30, comma separated)

Step 1 / 55

Merge sort splits the list in half again and again, then merges the sorted halves back together.

comparing
swapped / moved
pivot / minimum
sorted

JavaScript

1function mergeSort(arr) {
2  if (arr.length < 2) return arr;
3  const mid = arr.length >> 1;
4  const left = mergeSort(arr.slice(0, mid));
5  const right = mergeSort(arr.slice(mid));
6  const out = [];
7  while (left.length && right.length) {
8    out.push(left[0] <= right[0] ? left.shift() : right.shift());
9  }
10  return [...out, ...left, ...right];
11}

Tip: use the arrow keys to step and the space bar to play or pause.

Loading animation...

Merge Sort Visualization and Animation

Split the list in halves, sort each half, then merge them back in order. Split the list into two halves until each part has one value. Merge two sorted halves by always taking the smaller front value. Keep merging until one sorted list remains. Time complexity: O(n log n). Space complexity: O(n). Stable and predictable, so it is behind Array.prototype.sort in several engines. Stability keeps equal table rows in their original order.

How to use Merge Sort Visualizer

Split the list into two halves until each part has one value.
Merge two sorted halves by always taking the smaller front value.
Keep merging until one sorted list remains.
Press Play, or step through with the arrow buttons and change the input to see how it reacts.

Questions

What is Merge Sort?

Split the list in halves, sort each half, then merge them back in order.

What is the time complexity of Merge Sort?

Time: O(n log n). Space: O(n).

Where do front-end developers use Merge Sort?

Stable and predictable, so it is behind Array.prototype.sort in several engines. Stability keeps equal table rows in their original order.

Does this upload my data?

No. This converter runs in your browser for ordinary use, so the input is not sent to a backend by this tool.

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