The best cryptographic audit log solutions in 2026

The market for cryptographically verifiable audit logs is small and oddly shaped: a couple of managed services, several excellent open-source building blocks, one high-profile retirement, and a lot of ordinary logging products wearing the word "immutable" loosely. This guide compares the real options. One disclosure before any of it: Sigilbase is our product, so read that entry with the appropriate discount, and note that its claims are the kind you can check rather than take from us.

What actually separates these tools

Every product below can store an event. The differences that matter show up under hostile questioning, and they reduce to one dividing line and a handful of secondary questions. The dividing line: can someone who does not trust the operator verify the records independently, offline, with an open tool? If verification means calling the vendor's API or believing their dashboard, the trust has moved, not disappeared. The secondary questions: does it produce per-event inclusion proofs and between-export consistency proofs, can checkpoint roots be anchored outside the operator's reach, who holds the signing keys, what is the scope of what gets protected, and how much of your engineering time does it consume to run.

Sigilbase

Sigilbase is a managed audit log built around one idea: the evidence should not require trusting Sigilbase. Applications write events to a REST API with idempotent writes and batch ingestion; every event is SHA-256 hash-chained to the one before it; every few minutes the recent events are sealed into a Merkle checkpoint whose root is signed with an Ed25519 key. The whole history, or any range, exports as a self-contained evidence bundle: events, chain, per-event inclusion proofs, signed checkpoints, and public keys in one file. An auditor verifies the bundle with a standalone open-source verifier that runs offline, needs no account, and deliberately shares no code with the service, so a modified, deleted, or reordered event fails verification and the failure names the sequence number. Retention is forever on every plan, ingestion never stops for billing, and no cryptographic feature is plan-gated.

The honest caveats: Sigilbase is young, currently onboarding early-access teams, and it is purpose-built for application audit events rather than a general database, so it will not also be your analytics store or your debug log. Best for teams that need application audit trails an auditor, regulator, or counterparty can verify without taking anyone's word, and would rather integrate an API than operate ledger infrastructure.

immudb

immudb is an open-source immutable database from Codenotary, offering key-value and SQL interfaces over a Merkle-tree-backed store, with client libraries that cryptographically verify server responses so a tampering server can be caught by its own clients. It is a genuine database, fast, self-hostable, and widely deployed, and it is probably the strongest open-source option if what you want is verifiable storage under your own control.

The caveats are the flip side of being a database rather than an audit product: you design the event semantics, run and scale the server, own the key story, and, most importantly, build the narrative an external auditor can follow, since "our database verifies itself to our own clients" takes explaining in a way a self-contained evidence bundle does not. Best for engineering teams that want self-hosted verifiable storage as a component and are comfortable owning the rest.

Google Trillian

Trillian is the verifiable Merkle-tree log that underpins Certificate Transparency, which means it has operated under adversarial conditions at internet scale for the better part of a decade. It provides the primitives of this whole field, inclusion proofs and consistency proofs over an append-only log, with unmatched pedigree.

Trillian is infrastructure, not product. You bring the personality layer that defines what entries mean, the monitors that watch for equivocation, the storage backend, and everything an auditor would touch. Best for platform teams building transparency systems in the Certificate Transparency mould, rather than teams that need an audit trail for their application this quarter.

Azure Confidential Ledger

Azure Confidential Ledger is Microsoft's managed tamper-evident ledger, built on the Confidential Consortium Framework, with the distinguishing feature that the service runs inside hardware-backed secure enclaves, putting the ledger's operation outside the reach of Microsoft's own administrators. It issues cryptographic receipts for written entries that can be verified against the ledger.

It is Azure-native, which is its strength and its boundary: natural if your estate and your compliance posture already live in Azure, and its trust model leans on confidential-computing hardware attestation as much as on independently recomputable structure, which is a different conversation to have with an auditor. Best for Azure-committed organisations that want a managed ledger primitive from their existing cloud.

AWS CloudTrail log file integrity validation

CloudTrail with log file integrity validation enabled delivers hourly digest files, hashed and signed, so you can prove CloudTrail's own log files were not modified after delivery. If you run on AWS, turn it on; it costs nearly nothing.

It earns its place on this list mostly to mark its scope, because it is regularly mistaken for an application audit trail. CloudTrail records AWS API activity: who changed a security group, who assumed a role. It does not and cannot record who approved an invoice or edited a customer record inside your application, and its protections do not extend to logs your application writes elsewhere. Best as a baseline for AWS control-plane accountability, alongside, not instead of, an application audit log.

Sigstore Rekor

Rekor is the transparency log of the Sigstore project, built on Trillian, recording signatures over software artefacts so that anyone can verify what was signed and when. Within its niche, software supply chain provenance, it is excellent and increasingly the default. It is not a general audit log and does not aim to be; it appears here because teams searching this category sometimes actually need Rekor, and the reverse. Best for signing and verifying software artefacts, not business events.

A cautionary entry: Amazon QLDB

Amazon QLDB deserves a paragraph precisely because you can no longer buy it. AWS's managed ledger database, with hash-chained journals and cryptographic verification built in, was deprecated and reached end of support on 31 July 2025, with AWS pointing migrating customers to Aurora PostgreSQL, which has no equivalent built-in verification. Teams that adopted QLDB for records meant to stay verifiable for a decade spent 2025 migrating them. The lesson buyers should carry forward: audit records outlive products, so weight exportability and open, offline verification heavily, because they are what make records survive their vendor. It is also, we would note, an argument for verifiers that live in open source rather than inside a service.

The comparison at a glance

Choosing between them

The scenarios sort themselves fairly cleanly. If you need your application's audit trail to survive an auditor's or counterparty's scrutiny without a build project, that is the job Sigilbase was built for. If you want verifiable storage fully under your own roof and have the engineers to own it, immudb. If you are building transparency infrastructure as a product, Trillian. If your world is Azure, Confidential Ledger is worth evaluating first. Enable CloudTrail validation regardless, and reach for Rekor when the artefacts are software. And if you are tempted to build the whole thing yourself, our guide to implementing provable audit logs lays out honestly what that takes. If the evaluation is happening because enterprise procurement asked about your audit trail, the enterprise audit logs page maps those expectations to this design.

Whichever you evaluate, put the same question to it that an auditor will eventually put to you, covered in depth in our tamper-evident audit logs explainer: if a record had been quietly changed last year, who would have caught it, and would they have needed to trust anyone to do so?