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LedgerSync gives you one API for your users’ bank data. You link an account once, and we return accounts, balances, transactions, and statements as clean JSON — no matter which bank or which underlying data source is behind it. Under the hood we pull from three sources and route between them for you:

Finicity

Broadest US coverage, with bank OAuth where the institution supports it.

MX

An alternate aggregator that catches banks Finicity misses.

FDE

LedgerSync’s proprietary credential-based extraction, for banks neither aggregator covers.
You never pick a source. When you initiate a connection, v3 chooses the right one server-side from our institution catalog. There is no source parameter — the id you get back (like con_FINICITY_41294 or con_MX_1224) tells you which one answered.

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The data model

Everything hangs off four nested objects. Learn these once and the rest of the API reads naturally.
ObjectWhat it is
ClientYour record of one end-user. You set external_id; our id looks like cli_01HXYZ....
ConnectionOne linked bank for a Client. A Client can have many.
AccountA checking, savings, card, or loan account exposed by a Connection.
Transaction / StatementThe actual data on an Account.
Reads are Client-scoped — pass client_id on every read call. For example: GET /v3/accounts?client_id=cli_...&connection_id=con_FINICITY_41294.

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How linking works, in one breath

1

Create a Client

Your end-user, keyed by your own external_id.
2

Initiate a Connection

POST /v3/clients/{id}/connections with an institution_id. You get a 202 and an operation_id to poll.
3

Hand off the widget

Open the returned widget_url in the user’s browser. They pick their bank, sign in, and choose accounts. You never see their credentials.
4

Read the data

Once the connection goes active, store the canonical con_... id and read accounts, transactions, and statements.
The full walkthrough lives in Connect a bank.

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Start here

Quickstart

From a sandbox key to live transaction data in a few requests.

Connect a bank

Initiate, hand off the widget, and read back accounts.

Webhooks

Get told the moment a connection goes active, fails, or refreshes.

Errors

One error envelope, one field to branch on: code.

API Reference

Every endpoint, field, and response, in full.

Authentication

Bearer keys, sandbox vs. live, and the trace header.

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Everything is JSON over HTTPS

No SDK required. Send and receive JSON, authenticate with a Bearer key, and read the X-LS-Trace-Id header on every response for support. Sandbox is one key away — grab an sk_test_... key, point at https://api-sandbox.ledgersyncappv2.com/v3, and link the built-in FinBank test bank with no MFA.
Sandbox smoke test
curl https://api-sandbox.ledgersyncappv2.com/v3/institutions?q=chase \
  -H "Authorization: Bearer sk_test_..."
When you’re ready to try a full link end to end, head to the Quickstart.