Product
Limits, and whose they are
Last updated August 3, 2026
Two different things get called a limit. One is ours — a number we chose, which differs by plan and which we can change. The other belongs to Apple, Google, or Microsoft, applies to everyone, and no plan changes it. This page keeps them apart, because being told to upgrade for something an upgrade cannot fix is worse than being told no.
What your plan limits
Connected accounts, and nothing else. A connected account is one mailbox or Apple ID you have authorized — for example a personal Gmail, a work Microsoft 365 account, and an iCloud account is three.
- Personal — up to 3 connected accounts, up to 3 active sync rules.
- Business and Enterprise — unlimited connected accounts, unlimited active sync rules.
How often you sync is not limited, and neither is how much moves. There is no cap on the number of syncs, contacts, or calendar events on any plan. A 40,000-contact address book on Personal is fine. If a sync stops short, it is one of the ceilings below and not your plan.
During the Beta 1 program these plan limits are published but not enforced, so you may connect more accounts than your plan includes. We will tell you before that changes.
What your providers limit
These come from Apple, Google, and Microsoft. We work around them where a workaround exists and say so when one does not. We cannot raise them, and neither can a different SyncString plan.
- iCloud contacts per address book — 10,000 per response
- Apple returns at most 10,000 records in a single CardDAV listing. SyncString pages past this with RFC 6578 sync-collection, so larger address books do read in full — an account of 10,362 contacts reads completely. Very large books simply take more requests.
- Google and Microsoft 365 contacts per sync — 10,000 per connection
- Google People and Microsoft Graph paginate, and SyncString stops at 10,000 records per connection in a single pass. A read that stops here says so rather than looking complete.
What SyncString limits for technical reasons
Ours, but not commercial — these are engineering ceilings that apply on every plan. Upgrading does not change them. If one is getting in your way, tell us; that is useful information rather than an upsell.
- iCloud address books scanned — 25 per account
- SyncString reads up to 25 address book collections per iCloud account. Accounts with more are unusual; tell us if you have one.
- Records per downloadable backup dataset — 10,000 per dataset
- A downloadable backup includes up to 10,000 records per dataset. A backup that reaches this limit warns you that it is partial.
- Addresses handed to your mail or messaging app — 100 per Contact Group action
- Contact Groups pass up to 100 addresses at a time to your own email or messaging app, because longer lists are silently truncated by the apps themselves. The group's real size is always shown in full — use Copy for larger lists.
- iCloud calendars in a recovery backup — Not included yet
- A SyncString recovery backup includes iCloud contacts but not iCloud calendars. Contacts read over CardDAV; calendar backup needs CalDAV, which is not built yet. Any backup that leaves them out says so. Apple's own calendar export covers this in the meantime.
- Recovery backup retention — 30 days
- An encrypted recovery backup can be downloaded for 30 days after it is created, then it is deleted.
When a limit is reached
A read that stops short says so. SyncString never presents a partial result as a complete one — if a provider cut a read off, or refused part of it, the sync status names what happened and how many records were affected. A silently short contact list is the failure we most want to avoid, because a Contact Group built from one quietly misses people.
Questions
If something here does not match what you are seeing, that is a bug worth reporting rather than an expected difference. Compare plans or return to the overview.
7 published ceilings. This page is generated from the same configuration the product enforces, so it cannot describe a limit we do not apply.