Overledger is the product that put Quant on the map. Quant describes it as a universal API connector that provides secure interoperability between traditional financial systems and blockchain networks [1]. This guide explains what that means in practice, how developers get access, what it costs, and where Quant says it has been used. As always, we separate Quant's own claims from independently confirmed facts, and we give no investment advice.
The problem Overledger tries to solve
Every blockchain has its own data formats, signing methods and programming interfaces. A bank that wants to touch several of them would normally need to build and maintain separate integrations. The Blockworks token filing summarises Quant's pitch: blockchain implementations were difficult for enterprises and governments to adopt, and Overledger was designed to remove barriers to communication across multiple blockchains [2].
Overledger's answer is a common layer. Applications talk to Overledger's APIs using familiar web standards, and Overledger handles the specifics of each underlying ledger. The same filing says Overledger APIs let users issue, connect and monitor assets on any blockchain without blockchain expertise, and that Overledger is described by Quant as a blockchain operating system that lets applications function across multiple blockchains [2]. 'Without blockchain expertise' and 'any blockchain' are Quant's descriptions; the set of supported networks changes and should be checked in Quant's current documentation.
How it works at a high level
Think of Overledger as a translator and router. A developer registers an application, receives credentials, and makes API calls. The filing states that Overledger APIs use OAuth 2.0 client-credentials authorisation with short-lived JWT bearer tokens, and that API keys are created by registering an application on Quant Connect [2]. These are mainstream enterprise security patterns, which is part of the appeal to banks.
Quant's Overledger 2.0 release moved functionality out of software development kits and into APIs, added OAuth 2.0 for single sign-on and supports Open API 3 standards for developer workflow [2]. An older release note from Quant describes using the Overledger Payment API to transact and settle between different digital asset types in two API calls [3]. That is a description of a design goal as of that release, not a statement about current volumes.
Overledger is also described as a managed service: the filing says network nodes are secured and updated by Quant [2]. In other words, customers use Quant's platform rather than running the infrastructure themselves.
Access, KYC and fees
Overledger is not an open, permissionless protocol. Per the filing, the platform may only be accessed using an API key, developers working on mainnet networks need a paid plan and a KYC check, and Quant can disable dormant login credentials unused for more than 180 days [2].
On fees, the filing says developers seeking MainNet access under the Overledger 2.1.5 release paid a £100 annual licence fee in QNT using MetaMask [2]. Kraken adds that the annual fee was introduced on 10 December 2021 and that Quant's FAQ says platform fees can also be paid in US dollars or through a QNT subscription [4]. If you are wondering what links Overledger to the QNT token, this is the documented link: QNT is one way customers can pay for Quant services.
Pricing changes. Check Quant's own pricing pages for current terms before relying on any figure here.
Where has Overledger been used?
Quant says the infrastructure used in Project Rosalind, the Bank for International Settlements and Bank of England retail CBDC experiment, became available to businesses as the Overledger Platform in June 2023 [5]. The BIS describes Rosalind as an experiment that developed 33 API functionalities and explored more than 30 retail CBDC use cases, and notes the project was purely experimental [6]. The BIS text we reviewed does not name Quant, so Quant's role rests on Quant's own statement.
More recently, Quant announced it was selected by UK Finance and a consortium of banks to provide the technology behind the GBTD tokenised sterling deposits project [7], and the Bank of England lists both Quant and GBTD among its Synchronisation Lab participants [8]. The Clearing House in the United States announced Quant will provide the interoperability and orchestration layer for its On-Chain Money Initiative, expected to be available in the first half of 2027 [9]. See our tracker for dates, statuses and source links for each.
Notice the pattern: several of these are pilots, labs or announcements, not proof of large-scale production usage. The Bank of England states its Lab is not a regulatory sandbox and will not support real-money payments [8].
Overledger and the QNT token: what is the relationship?
It is easy to assume that every bank using Overledger must buy QNT. The documented picture is more limited. QNT can be used to pay licence fees [2], but Quant's FAQ also allows payment in US dollars [4]. And the filing is explicit that QNT carries no governance rights, no right to dividends and no claim on Quant's revenue [2]. Commercial success of Overledger therefore does not automatically flow to token holders. We offer no view on what, if anything, it means for price.
Questions to ask when you see an 'Overledger partnership' headline
Our tracker applies these questions: an entry appears only when we can link an official or primary source, and its status is labelled live, pilot, announced or completed.
- Is it a signed commercial deployment, a pilot, or a test environment?
- Is it announced by the partner itself, or only by Quant or a third-party blog?
- Is there a go-live date, and has it passed?
- Does the announcement say anything about paying in QNT? Often it does not.
- Is the term 'partnership' being used loosely for a supplier relationship?
Where to learn more
Quant's developer pages and documentation are the authoritative source for current technical details [10]. For independent summaries, start with the Blockworks filing and Kraken's explainer, both linked below.
Frequently asked questions
What does Overledger do?
Quant describes Overledger as a universal API connector that provides secure interoperability between traditional financial systems and blockchain networks, so applications can use one set of APIs rather than separate integrations per blockchain.
Is Overledger decentralised?
No. It is a managed platform run by Quant Network Ltd. Access uses API keys, mainnet use needs a paid plan and a KYC check, and network nodes are secured and updated by Quant, per the Blockworks filing.
Do you need QNT to use Overledger?
Not necessarily. Licence fees have been payable in QNT, but Quant's FAQ, as reported by Kraken, says platform fees can also be paid in US dollars or through a QNT subscription.
Who uses Overledger?
Quant has announced work with UK Finance's GBTD project, the Bank of England's Synchronisation Lab, The Clearing House and others. Many are pilots or announcements. See our tracker for statuses and primary sources.
Sources
- Quant: Overledger Platform
- Blockworks Token Transparency filing for Quant
- Quant: Introducing Overledger 2.0.5
- Kraken Learn: What is Quant (QNT)?
- Quant press release, 27 Jun 2023: Overledger Platform and Project Rosalind
- BIS: Project Rosalind completion release (16 Jun 2023)
- Quant: selected to deliver UK tokenised sterling deposits infrastructure (26 Sep 2025)
- Bank of England: Synchronisation Lab
- The Clearing House: partners with Quant on On-Chain Money (24 Sep 2026)
- Quant: developers