Developers

Developer API

Version 1 · Last updated: October 8, 2026

1. Authentication

Send your token in the Authorization header. Tokens start with ms_live_, are shown once when you create them, and are stored by us only as a SHA-256 hash — a lost token cannot be recovered, only revoked and replaced. You can hold up to five, and revoke any of them at any time in the same screen.

curl https://metalstrength.fit/api/v1/me \
  -H "Authorization: Bearer ms_live_YOUR_TOKEN"

Treat a token like a password: it reads your training history. Never put it in a page other people can open, a public repository, or a shared spreadsheet.

2. Basics

Base URL	https://metalstrength.fit/api/v1
Format	JSON, UTF-8. Dates are YYYY-MM-DD (your own calendar day); instants are ISO 8601 UTC.
Units	Body data is always metric (kg, cm, %). A workout's weights are in the workout's own unit (kg or lb).
Access	Read-only. Premium accounts only; when Premium ends, tokens stop working until it is renewed.
Rate limit	120 requests per minute per token.
CORS	Allowed from any origin (the token, not a cookie, is the credential).

3. Errors

Every error has an HTTP status and the same body:

{ "error": { "code": "premium_required", "message": "The API is part of Metal Strength Premium." } }

Status	code	Meaning
401	unauthorized	Missing, unknown or revoked token.
403	premium_required	The account has no active Premium.
404	not_found	No such workout on this account.
429	rate_limited	Over 120 requests a minute. Wait and retry.
500	server_error	Our side. Retry with a short backoff.

4. GET /me

Who the token belongs to, and the profile numbers your data is read against.

{
  "data": {
    "id": "5f1c…",
    "displayName": "Sam",
    "sex": "male",
    "age": 31,
    "heightCm": 180,
    "bodyweightKg": 82.4
  }
}

5. GET /workouts

Your saved workouts, newest first.

Parameter	Meaning
since	Only workouts trained on or after this day (YYYY-MM-DD).
until	Only workouts trained on or before this day.
limit	1–100, default 50.
offset	Skip this many. paging.next gives the next offset, or null at the end.

{
  "data": [
    {
      "id": "9a0e…",
      "performedOn": "2026-10-08",
      "savedAt": "2026-10-08T18:52:11.204Z",
      "name": "Push A",
      "program": "Push Pull Legs",
      "unit": "kg",
      "durationSec": 3120,
      "exercises": [
        {
          "exerciseId": "barbell-bench-press",
          "name": "Barbell Bench Press",
          "supersetId": null,
          "sets": [
            { "kind": "warmup", "done": true, "reps": 5, "seconds": null, "weight": 40, "rpe": null, "note": null },
            { "kind": "working", "done": true, "reps": 8, "seconds": null, "weight": 80, "rpe": 8, "note": null }
          ]
        }
      ],
      "heartRate": {
        "avg": 124, "max": 168, "min": 82, "maxHr": 186,
        "zoneSeconds": [840, 1260, 690, 300, 30],
        "series": [96, 101, 118, 0, 131],
        "seriesStepSec": 30
      }
    }
  ],
  "paging": { "limit": 50, "offset": 0, "next": 50 }
}

Field	Meaning
sets[].kind	warmup, working, drop or failure.
sets[].done	Whether the set was ticked off. Only done sets count as work.
sets[].seconds	Set for timed sets (holds, intervals) instead of reps; otherwise null.
sets[].rpe	Effort, 5–10 in half steps, or null. Sets logged as RIR are stored as RPE = 10 − RIR.
heartRate	From the watch, via the phone's health app; null when none was recorded. zoneSeconds are zones 1–5 by share of maxHr (<60, 60–70, 70–80, 80–90, ≥90%). series is one reading per seriesStepSec from the start, 0 where there was none.

6. GET /workouts/{id}

One workout, in the same shape, under data.

7. GET /body

Weigh-ins, body-fat readings and tape measurements, oldest first. Accepts since and until.

{
  "data": {
    "weight": [ { "date": "2026-10-07", "kg": 82.4 } ],
    "bodyFat": [ { "date": "2026-10-01", "percent": 15.2 } ],
    "measurements": [ { "date": "2026-10-05", "site": "waist", "cm": 84.5 } ]
  }
}

site is one of neck, shoulders, chest, waist, hips, arm_left, arm_right, forearm_left, forearm_right, thigh_left, thigh_right, calf_left, calf_right.

8. Terms of use

• The API is for reading your own data. Do not use a token to build a service that holds other people's Metal Strength data.
• Keep tokens secret and revoke any you no longer use. You are responsible for what is done with a token you created.
• Version 1 will not change in a way that breaks a working script. New fields may be added; anything removed or renamed will come as a new version, announced here first.
• Abuse (scraping beyond the rate limit, sharing tokens) can get tokens revoked. The Terms of Service apply.

9. Privacy

The API returns only what your account already holds, to whoever holds your token. We keep the token's hash, its name, and when it was created and last used — listed in Download my data and deleted with your account. See the Privacy Policy.