What is a warrant canary, and why does it matter?

A warrant canary is a regularly-published, PGP-signed statement that a service provider has not received certain types of legal process — most commonly a National Security Letter, a gag order, or a bulk surveillance demand. The canary continues until it stops. The absence of the next scheduled canary is the signal that something changed. This page explains the mechanism, walks through PGP verification, and lists the providers who maintain one in 2026.

Updated 2026-05-03 · Author: Cryptoservers Engineering

See the live Cryptoservers canary → How to verify a canary

Mechanism

How a warrant canary works — the legal logic

The warrant canary depends on a specific asymmetry in compelled-speech doctrine. Many surveillance statutes — 18 USC §2709 in the United States (the National Security Letter authority); analogous provisions in the UK Investigatory Powers Act 2016 (§133 non-disclosure); equivalents in other 14-Eyes jurisdictions — include non-disclosure clauses that prevent the recipient of an order from talking about it. Those clauses compel silence. They do not, in most jurisdictions, compel the recipient to actively make a false affirmative statement.

That distinction is what the canary exploits. A provider publishes "we have not received an NSL as of [date]" on a fixed cadence — weekly, monthly, quarterly. As long as the statement remains true, publication continues. If the provider receives an order, they cannot say so directly (gag order). But they can stop publishing the affirmative statement. The next scheduled canary either does not appear, or appears with the relevant clause removed, or appears with different language. That absence — that change — is information that the gag order cannot suppress.

The Cryptoservers canary, published at /canary/, follows this pattern. Every Monday we re-sign a statement covering the week ending the prior Sunday. The signed statement enumerates: NSLs received (target: zero), gag orders received (target: zero), bulk-retention orders received (target: zero), per-jurisdiction order counts (Saint Kitts and Nevis, Iceland, Netherlands, Romania, Switzerland), DMCA notices received versus actioned, and abuse complaints received versus actioned. Five of the six numbers are expected to be zero in a normal week; the abuse and DMCA numbers are non-zero by design (we receive abuse complaints, and we publish how many).

The cadence matters. A canary published once a year carries less signal than one published weekly — the lag between coercion and the customer noticing is the freshness window. Weekly canaries reduce that window to seven days; daily canaries (rare, because they require key-handling at scale) reduce it to twenty-four hours. Quarterly canaries leave a three-month window in which a provider could be compromised before any external observer notices.

PGP verification

Verifying a PGP-signed canary — four steps

A canary that is not cryptographically signed is theatre. Verification takes four steps and about ninety seconds. The example below uses the Cryptoservers canary; the same procedure works for any provider that publishes a PGP-signed canary.

Step 1 — Get the public key from the provider. Cryptoservers publishes the public PGP key at /pgp/. The key fingerprint is documented on multiple pages of the website (about, canary, pgp, footer) so a single-page tampering attempt is detectable. Cross-reference the fingerprint against multiple sources — archive.org snapshots, the Wayback Machine, third-party PGP keyservers — before you trust it.

curl -O https://cryptoservers.io/pgp/cryptoservers-pubkey.asc
gpg --show-keys cryptoservers-pubkey.asc

Step 2 — Import the key. Import into your local GnuPG keyring. The key remains in your local store — no upload required, no third-party trust needed.

gpg --import cryptoservers-pubkey.asc

Step 3 — Download the signed canary text. The canary at /canary/ is rendered HTML, but the underlying signed file is also available as a clearsigned .asc — visible at the bottom of the canary page or directly via the storage path. For the purposes of this example, save it as canary.asc in your working directory.

curl -O https://cryptoservers.io/canary/latest.asc

Step 4 — Verify the signature. Run gpg --verify against the .asc file. A "Good signature" line confirms two things: the canary was signed by the holder of the imported key, AND the canary text has not been altered since signing. A failed verification means the file has been modified, the signature is invalid, or the key does not match — treat the canary as untrusted and investigate further.

gpg --verify canary.asc

# expected:
# gpg: Good signature from "Cryptoservers Ltd. <[email protected]>"
# gpg: Primary key fingerprint: 4DCF 5D6D 10AF F2AA 47E2  070E A62A EDAF 647E E3E6

If you have not used GnuPG before, install it first: `apt install gnupg2` on Debian-family Linux, `brew install gnupg` on macOS, or download GPG4Win on Windows. The verification step itself is the same on every platform.

Active canaries

Hosts and organisations that maintain a warrant canary

Short list, verifiable. We have included historical examples (Apple 2013–2014, Reddit 2014–2016) for context — they are useful as case studies in how a canary signals change. Send us additions via /contact/ if you maintain a public canary not listed here.

Provider / project	Cadence	First published	Status	Notes
rsync.net	Quarterly, PGP-signed	2014	Maintained	One of the earliest commercial canaries. Includes Bitcoin block-hash as a freshness anchor.
Cryptoservers	Weekly, PGP-signed (every Monday)	2024	Maintained	Per-jurisdiction order counts (KN, IS, NL, RO, CH) plus DMCA, abuse, NSL and gag-order statements.
Bahnhof (transparency report)	Annual transparency report (not a canary in the strict sense)	2014	Active transparency reporting	Swedish ISP. Publishes detailed transparency stats; the canary-style attestations are scattered through the integrity page rather than a single signed document.
The Tor Project	Annual	2014	Maintained	Re-affirmed annually. One of the longest-running organisational canaries.
Apple (historical)	Removed in 2014 — historical example, not current	2013	Removed (2014) — historical	Apple's November 2013 transparency report contained the canonical "Apple has never received an order under Section 215" canary statement. The line was conspicuously absent from the September 2014 report. Apple has not commented publicly on the change.
Reddit (historical)	Removed in 2016 — historical example, not current	2014	Removed (2016) — historical	Reddit's 2014 transparency report carried a National Security Letter canary. The 2015 report removed the language. The administrator who maintained the canary commented publicly that he could not say more.

We deliberately keep this list short. A long aspirational list dilutes the signal — the value of a canary is that it is verifiable, and verification at scale is expensive. We update the list when we change it; the dateModified field on this page reflects the most recent verification pass.

Honest section

What does a missing canary actually mean?

Honest answer: less than the marketing copy implies. The dominant cause of a missed canary in the past decade has not been the receipt of a National Security Letter — it has been administrative oversight. The engineer responsible was on vacation, the cron job hit a credential rotation, the DNS for the canary subdomain expired, the company forgot. A single missed renewal is weak signal at best.

What turns weak signal into strong signal is corroboration. Look for:

A canary that misses its scheduled renewal and subsequently appears with materially altered language (clause removed, jurisdiction count changed, scope narrowed).
A canary failure that coincides with public reporting of a legal matter involving the provider.
A PGP key change accompanying the canary disruption — particularly if the new key was published without the multi-source fingerprint cross-reference that the original key had.
Organisational silence — no public statement explaining the disruption, no acknowledgement on social media, no response to direct customer queries.
Sudden unavailability of the canary URL itself, especially if cached versions on archive.org are also removed.

Apple's 2014 canary removal is the canonical case study. The September 2013 transparency report contained the line "Apple has never received an order under Section 215 of the USA Patriot Act." The September 2014 transparency report did not. Apple issued no public statement explaining the change. Privacy researchers (Christopher Soghoian, then with the ACLU; Glenn Greenwald at The Intercept) flagged the absence within days. The signal was weak at first — could have been an editorial change — but the absence persisted across subsequent reports, and Apple's general counsel did not subsequently re-affirm the canary statement when directly asked. Two years later the consensus interpretation in the privacy-research community was that Apple had received a Section 215 order. Apple has never confirmed or denied this.

The right interpretation of a missed canary is "investigate further", not "the provider has been served". Canaries are evidence in the absence of deception, not proof in its presence.

Limits

Limitations of canaries as a signal

Three honest limits that you should weigh before treating a canary as cryptographic proof of provider integrity.

1. The legal theory is loophole-dependent. The canary exploits a doctrine that gag orders compel silence rather than affirmative falsehood. That doctrine has not been definitively tested for every surveillance statute in every jurisdiction. The Stanford Law Review and other legal scholars have argued both sides. A determined prosecutor could plausibly argue that compelling continued affirmative publication of "we have not received" is itself part of a non-disclosure obligation, and that ceasing publication is a breach of the gag. The legal theory has held up so far in published US case law, but it has not been litigated to definitive resolution. Other jurisdictions are even less tested.

2. Unsigned canaries are useless. A canary that is not signed with a verifiable PGP key — or that uses a key whose fingerprint cannot be cross-referenced against multiple independent sources — is theatre. An adversary who controls the provider's website can substitute a forged "everything is fine" canary and there is no way to detect the substitution. The PGP signature is what makes the canary load-bearing. Unsigned text is not a canary, no matter what it says. Verify before you trust.

3. Lapsed canaries are ambiguous. When a canary stops being renewed, the interpretation depends on what else is happening. A lapsed canary plus organisational silence plus a key change is strong signal. A lapsed canary alone is weak — it could mean the engineer is on vacation. A canary that never started is no signal at all. The burden of disambiguation falls on the customer; the provider can only honestly publish what they can honestly publish.

Treat canaries as one cultural-integrity signal among several, not as a security guarantee. A canary tells you that a provider thinks coercion is a real enough risk to invest engineering effort in pre-publishing the contradiction signal. That is meaningful. It is not the same thing as cryptographic proof.

FAQ

Warrant canary — frequent questions

What is a warrant canary?

A warrant canary is a regularly-published statement that a service provider has not yet received certain types of legal process — most commonly a National Security Letter, a gag order, or a bulk surveillance demand. The canary is published in the affirmative ("we have not received…") on a fixed cadence (weekly, monthly, quarterly). The legal logic is asymmetric: a gag order can compel silence about a received order, but most jurisdictions cannot compel a person to make an affirmative false statement. So the warrant canary continues until it stops — and the absence of the next scheduled canary is the signal that something has changed.

How does a warrant canary actually work in law?

The mechanism depends on a specific gap in compelled-speech doctrine. Many surveillance statutes — 18 USC §2709 for US National Security Letters, similar provisions in other 14-Eyes jurisdictions — include non-disclosure clauses preventing the recipient from talking about the order. Those clauses compel silence. They do not, in most cases, compel the recipient to actively lie. So if a provider has been publishing "we have not received an NSL" weekly for two years, and one week the statement does not appear (or its language changes), that absence is itself information that the gag-order regime cannot suppress. The legal theory has not been definitively tested in court for every statute in every jurisdiction — see "Limitations" below for the honest caveats.

Is a warrant canary legally binding?

Not in the contractual sense. A canary is a unilateral, public attestation by the provider, not a covenant with any specific customer. What makes it useful is that (a) it is signed with the provider's PGP key, so anyone can verify it came from the same key that signed every prior canary; (b) it is timestamped, so the absence of a renewal is detectable; and (c) the provider's reputation and their threat model are aligned around its continued publication. A canary is more like a firmware-version attestation than a contract — useful evidence in the absence of a deception, useless once you suspect a deception.

How do I verify a PGP-signed warrant canary?

Four steps. (1) Download the provider's public PGP key from their website (Cryptoservers publishes ours at /pgp/ — verify the fingerprint matches the one published on the warrant-canary page itself). (2) Import the key with `gpg --import cryptoservers-pubkey.asc`. (3) Download the signed canary text. (4) Run `gpg --verify canary.asc` to check the signature. Successful verification proves: the canary was signed by the holder of the published key, AND the canary text has not been modified since signing. If verification fails, treat the canary as untrusted. Cross-check the fingerprint against multiple sources (the provider's site, archive.org snapshots, third-party PGP keyservers) to defend against a key-substitution attack.

What does it mean when a canary "dies"?

Canary death — the absence of an expected scheduled renewal — is most often administrative oversight, not the receipt of an NSL. Real-world history: most canary-renewal failures in the last decade have been because the engineer responsible was on vacation, the cron job hit a credential-rotation, or the company forgot. The signal is genuinely ambiguous. If a canary fails to renew, the right interpretation is "investigate further" rather than "the provider has been served". Cross-reference: ask other customers, check archive.org, look for community discussion on the relevant subreddits or hacker forums. A single missed canary is weak signal; a missed canary plus organisational silence plus a key change plus removal of the canary URL is strong signal.

Why don't bigger providers publish canaries?

Several reasons, none of them flattering. First, large publicly-traded providers face shareholder-litigation risk if a canary is interpreted as material non-public information — much easier to publish nothing than to publish a statement that might trigger a 10-Q disclosure debate. Second, the legal theory underlying canaries is unsettled: a provider's general counsel can plausibly argue that publishing one creates litigation exposure. Third, large providers receive enough surveillance demands that publishing a "we have not received" canary would be perjury immediately — at scale, the canary is incompatible with the operating reality. Smaller privacy-focused providers can credibly publish canaries because they receive few or no qualifying orders; very large providers cannot.

Are canaries useful, or are they security theatre?

Honest answer: they are useful as one signal among several, not as a security guarantee. A canary tells you that a provider thinks adversarial coercion is a real enough risk to invest engineering effort in pre-publishing the contradiction signal. That is meaningful cultural information about who you are dealing with. The canary itself is not cryptographic proof of non-coercion — it is cultural proof of coercion-aware operations. Combine canary publication with other signals (jurisdiction, ownership transparency, transparency reports, abuse-handling track record, PGP key continuity) for a meaningful overall picture. A canary alone is not enough; a canary plus everything else above is meaningful.

Where can I find a list of providers with active canaries?

The canonical reference is the Canary Watch project (originally maintained by EFF, now defunct as a centralised list since 2016) and the Wikipedia "Warrant canary" article, which maintains a partial list. We list the providers we know maintain active canaries in the table on this page — we have deliberately kept it short and verifiable rather than long and aspirational. The list shifts: Apple removed theirs in 2014, Reddit in 2016, Tumblr at various points. We update this page when we change the list. If you maintain a public canary and are not on this page, send us the URL through /contact/ and we will verify and add you.

Citations

Sources we relied on

See the live canary — verified weekly.

Cryptoservers re-signs the canary every Monday. The current statement, the archive of every prior week, and the PGP key for verification are all on /canary/.

See the live Cryptoservers canary Download the PGP key