bigfive-open

Open-source Big Five personality test — questions, scoring algorithm, and TypeScript types based on the public-domain IPIP-50 inventory. This is the engine behind bigfivepersonality.me, a free, anonymous, no-sign-up Big Five test.

---

Why

Existing open Big Five implementations are either heavy full-stack apps or unmaintained. This repo is the opposite — just the core (items + scoring) in plain TypeScript, zero runtime dependencies, so you can drop it into any project.

Use it to build:

• A personality test web app
• A research tool or survey
• A Discord / Slack bot
• A mobile app
• An internal HR / team-building tool

What's inside

src/
  data/questions.ts   # IPIP-50 items (public domain, with OCEAN + keying)
  scoring.ts          # reverse-score, raw score, 0–100 normalize, low/medium/high bands
  index.ts            # public API
tests/
  scoring.test.ts     # algorithm invariants

No React. No Next.js. No i18n framework. Just functions and types.

Install

# via git (until published to npm)
pnpm add github:KatherineGuoGuo/bigfive-open

Usage

import { QUESTIONS, calculateAllScores, type Answers } from 'bigfive-open';

// Collect user responses on a 1–5 Likert scale, keyed by question id
const answers: Answers = {};
for (const q of QUESTIONS) {
  answers[q.id] = 3; // user answer goes here
}

const scores = calculateAllScores(answers);
// {
//   E: { score: 50, rawScore: 30, level: 'medium' },
//   A: { score: 50, rawScore: 30, level: 'medium' },
//   C: { score: 50, rawScore: 30, level: 'medium' },
//   N: { score: 50, rawScore: 30, level: 'medium' },
//   O: { score: 50, rawScore: 30, level: 'medium' },
// }

Scoring details

• Items: 50 (10 per domain)
• Scale: 1 (Strongly Disagree) → 5 (Strongly Agree)
• Reverse-keying: minus-keyed items are flipped (1↔5, 2↔4, 3→3) before summing
• Raw score per domain: 10–50
• Normalized score: 0–100, rounded
• Level bands: low ≤ 35 · medium 36–65 · high ≥ 66

Scientific basis

The item pool is from the International Personality Item Pool (IPIP), a public-domain collection curated by Lewis R. Goldberg and colleagues for open psychological research.

• IPIP-50 source: https://ipip.ori.org/new_ipip-50-item-scale.htm
• Goldberg, L. R. (1992). The development of markers for the Big-Five factor structure. Psychological Assessment, 4, 26–42.
• Goldberg, L. R., Johnson, J. A., Eber, H. W., Hogan, R., Ashton, M. C., Cloninger, C. R., & Gough, H. G. (2006). The International Personality Item Pool and the future of public-domain personality measures. Journal of Research in Personality, 40, 84–96.

Disclaimer

This test is for self-reflection and educational purposes. It is not a clinical instrument and should not be used to diagnose mental-health conditions. For clinical use, consult a licensed psychologist and use a validated, scored inventory (e.g. NEO-PI-R).

Contributing

Contributions welcome. Easiest wins:

• Add translations — drop a new file under src/data/translations/<lang>.json (open an issue first)
• Report bugs in scoring or documentation
• Citations — if you've published work using this, PR a link

Please keep the core dependency-free.

Related

• Live demo — take the Big Five personality test (free, anonymous, no sign-up)
• The Big Five personality traits explained — the OCEAN model and each of the five dimensions
• How to interpret your Big Five scores — what low / medium / high mean per domain
• IPIP (authoritative source): https://ipip.ori.org/

License

MIT. The IPIP-50 item set is in the public domain.