What is the Wright–Fisher model?

A basic population genetics model that samples allele counts each generation with a binomial distribution.

What is genetic drift?

In finite populations, allele frequencies fluctuate by chance even under neutrality. Replicates reveal fixation/loss rates and distributions.

What is the difference between N and 2N?

Here, N is the diploid population size, and allele copies are treated as 2N (displayed on screen).

Genetic drift simulator (Wright–Fisher) | allele frequency drift

How to use (3 steps)

Select an example or enter N, p0, generations, and replicates.
If needed, add selection/mutation/migration in Advanced (you can keep defaults).
Click Run to see trajectories, distributions, and fixation/loss rates.

Inputs (N, p0, replicates)

Example (preset)

—

N (diploid population size)

2N = —（gene copies）

Initial frequency p0 (0–1)

Generations

Replicates

seed

Run settings Stop at absorption (stop_at_absorption)

Compute load: —

Advanced (selection, mutation, migration)

You can ignore details at first. Start with neutral drift to understand the dynamics.

Selection

s（-1〜1）

h（0〜1）

Mutation

μ（A→a）

ν（a→A）

Migration

m (migration rate)

p_source (source frequency)

Results (fixation/loss & distribution)

An example runs automatically. Change inputs and click Run to try other settings.

Visualization (trajectories & distributions)

Export (copy / CSV / JSON / share URL)

Include trajectories in JSON (sample for plotting)

How it’s calculated

Each generation samples the next allele count from a binomial distribution (Wright–Fisher).
Many replicates reveal fixation/loss rates and distributions.
Advanced mode applies selection/mutation/migration before sampling.

This is a model. Real populations are more complex, so use results as a guide.

FAQ

Is fixation probability always p0?

For neutral drift, p0 is a common guide, but selection changes it. You can check simulation results here as well.

Is N the number of individuals?

Here, N is the number of diploid individuals, and allele copies are treated as 2N (displayed).

How many replicates do I need?

It depends, but more replicates stabilize fixation/loss rates. Reduce replicates if it is heavy.

Are advanced options required?

No. Start with neutral drift to understand the dynamics.

Are my inputs sent anywhere?

All calculations run in your browser. Your data is not sent.

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