Reference

Limits

Your limits depend on your offers and apply to your whole account, across all your keys. Track your usage at any time with GET /v1/usage.

Limits by plan

Live and Historical stack: with both, you get the rights of both. What each offer includes and how to buy it: Plans and billing.

Limit	Sandbox	Live	Historical	Live + Historical
Billing	Free	Monthly subscription	One-time purchase, lifetime access	Monthly subscription + One-time purchase, lifetime access
Stream	10-minute delay	Real time	10-minute delay	Real time
Concurrent connections	1	5	1	5
Concurrent subscriptions	2	50	2	50
Custom configurations	1	25	1	25
History	Last 7 days	Not included	Full available depth	Full available depth
Monthly compute budget	50,000,000 units	Not included	20,000,000,000 units	20,000,000,000 units
Monthly export volume	Not included	Not included	20 GB	20 GB
REST requests per key	60 per minute	300 per minute	1,200 per minute	1,200 per minute

How limits are counted

Per account: connections, subscriptions and budgets are shared by all your keys. Creating more keys does not raise your limits.
Custom configurations: an indicator used on an instrument with parameters that differ from its defaults. For example, Fathom Trades with a minimum volume of 50 instead of 30. Each combination counts once, even if several subscriptions use it.
Compute budget: every access to history (a query, an export, or a subscription that starts in the past) consumes units: the number of trades read, times the indicator cost shown in the catalog. You can estimate that cost up front, for free.
Export volume: the amount of data your exports download.

The compute budget and the export volume renew at the start of every month (UTC), including with the lifetime access of the Historical offer. A request that would exceed them is rejected before it starts, with 429 QUOTA_EXCEEDED.

Technical limits

These are the same for every plan.

Item	Limit	If you exceed it
REST requests	Depends on your plan, per minute and per key	`429 RATE_LIMITED`
REST request body size	16 KB	`413`
Active keys	10 per account	`409 QUOTA_EXCEEDED`
Allowed instruments and IP addresses per key	32 of each	`400 INVALID_PARAMETERS`
Grace period when rotating a key	7 days at most	`400 INVALID_PARAMETERS`
Sign-in links	5 per hour per e-mail address, valid for 15 minutes	`429 RATE_LIMITED`
Browser stream token	Valid for 60 s, single use	Connection closed (`4001`)
`auth` message after the WebSocket opens	5 s	Connection closed (`4001`)
Message sent on the WebSocket	64 KB	Connection dropped
Subscription name (`sub`)	1 to 64 characters, unique on the connection	`error` `INVALID_PARAMETERS`
Resume from a cursor	Disconnects of up to about 15 minutes	`reset`, then a new snapshot
Data waiting to be sent (slow client)	256 KB, then 1 MB	Intermediate versions skipped, then connection closed (`4008`)
Client silence	30 s	Connection closed (`4008`)
Results per history page	1 to 10,000 (1,000 by default)	Next page through `next`
Calculation kept after the last unsubscribe	10 minutes	Warm-up (`warming`) on the next subscribe

Requests per minute

Each key can send a set number of REST requests per minute, depending on your plan. Unused requests accumulate up to that limit. Every response tells you where you stand:

HTTP

RateLimit-Limit: 1200
RateLimit-Remaining: 1197
RateLimit-Reset: 1

RateLimit-Remaining: requests available right now;
RateLimit-Reset: seconds until the full limit is restored.

Past the limit, the request is rejected with 429 RATE_LIMITED; the Retry-After header says how many seconds to wait. The SDK waits and retries automatically.

Track your usage

BASH

curl https://api.fathomcharts.com/v1/usage -H "Authorization: Bearer $FATHOM_CHARTS_API_KEY"

JSON

{
  "period": "2026-10",
  "resetsAt": "1793491200000000000",
  "plan": "live_history",
  "limits": {
    "computeBudget": 20000000000,
    "exportBytes": 21474836480,
    "restPerMinute": 1200,
    "historyDays": 36500,
    "delaySeconds": 0,
    "maxConnections": 5,
    "maxSubscriptions": 50,
    "maxCustomConfigs": 25,
    "realtime": true
  },
  "used": { "computeUnits": 1840233, "historyItems": 51207, "exportBytes": 734003200, "restRequests": 412 },
  "remaining": { "computeUnits": 19998159767, "exportBytes": 20740833280 }
}

plan: your offers, one of sandbox, live, history or live_history (both);
period and resetsAt: the current month and the date of the next renewal;
limits: the limits that apply to you. With a test key, these are the Sandbox limits. historyDays is 0 without history, and 36500 for the full available depth;
used and remaining: your usage this month and what you have left.