How to Seed Supabase with Realistic Test Data

The Problem

Every Supabase project starts the same way: you create beautiful tables, define RLS policies, and then sit there staring at an empty database. Writing manual INSERT statements is tedious, and tools like Faker.js require you to build an entire seed script from scratch, handle relational foreign keys yourself, and hope the data looks realistic enough for demos.

If you are working with a team, the problem multiplies. Everyone ends up with a different local dataset, QA tests against stale fixtures, and staging environments look nothing like production.

The Solution: MockHero API

MockHero is a single API call that returns realistic, relationally-consistent test data. Define your schema with 156+ field types, add ref fields to connect tables, and get back JSON you can pipe directly into Supabase. No libraries to install, no generators to maintain.

Quick Setup

curl -X POST https://api.mockhero.dev/api/v1/generate \
  -H "x-api-key: mh_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
  "tables": [
    {
      "name": "profiles",
      "count": 10,
      "fields": [
        { "name": "id", "type": "uuid" },
        { "name": "full_name", "type": "full_name" },
        { "name": "email", "type": "email" },
        { "name": "avatar_url", "type": "avatar_url" },
        { "name": "created_at", "type": "datetime" }
      ]
    },
    {
      "name": "posts",
      "count": 30,
      "fields": [
        { "name": "id", "type": "uuid" },
        { "name": "author_id", "type": "ref", "params": { "ref": "profiles.id" } },
        { "name": "title", "type": "sentence" },
        { "name": "body", "type": "paragraphs" },
        { "name": "published", "type": "boolean" }
      ]
    }
  ],
  "format": "json"
}'

Step-by-Step Guide

1. Install dependencies

npm install @supabase/supabase-js

2. Get your MockHero API key

Sign up at mockhero.dev/sign-up and copy your API key from the dashboard. The free tier gives you 1,000 rows per month.

3. Write the seed script

Create a file called seed.mjs in your project root:

import { createClient } from "@supabase/supabase-js";

const supabase = createClient(
  process.env.SUPABASE_URL,
  process.env.SUPABASE_SERVICE_ROLE_KEY
);

const res = await fetch("https://api.mockhero.dev/api/v1/generate", {
  method: "POST",
  headers: {
    "x-api-key": process.env.MOCKHERO_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    tables: [
      {
        name: "profiles",
        count: 20,
        fields: [
          { name: "id", type: "uuid" },
          { name: "full_name", type: "full_name" },
          { name: "email", type: "email" },
          { name: "avatar_url", type: "avatar_url" },
          { name: "created_at", type: "datetime" },
        ],
      },
      {
        name: "posts",
        count: 50,
        fields: [
          { name: "id", type: "uuid" },
          { name: "author_id", type: "ref", params: { ref: "profiles.id" } },
          { name: "title", type: "sentence" },
          { name: "body", type: "paragraphs" },
          { name: "published", type: "boolean" },
        ],
      },
    ],
    format: "json",
  }),
});

const { data } = await res.json();

const { error: profilesError } = await supabase
  .from("profiles")
  .insert(data.profiles);
if (profilesError) console.error("Profiles error:", profilesError);

const { error: postsError } = await supabase
  .from("posts")
  .insert(data.posts);
if (postsError) console.error("Posts error:", postsError);

console.log(
  "Seeded", data.profiles.length, "profiles and",
  data.posts.length, "posts"
);

4. Run the script

node seed.mjs

5. Verify in Supabase Studio

Open the Table Editor in your Supabase dashboard. You should see 20 profiles and 50 posts, each post correctly referencing a profile through the author_id foreign key.

Complete Example

The seed script above is complete and production-ready. For larger datasets, increase the count values and consider batching your Supabase inserts. MockHero handles the relational consistency automatically so every author_id maps to a real profiles.id.

Why MockHero vs Faker / Manual Seeds

• Relational data out of the box — ref fields guarantee foreign keys match across tables, no manual wiring.
• No code to maintain — your seed logic is a JSON schema, not hundreds of lines of JavaScript.
• Deterministic seeds — pass a seed parameter to get the same data every time, great for CI.

Get Started

MockHero offers a free tier with 1,000 rows per month, no credit card required. Sign up here and start seeding your Supabase project in under a minute.