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Cybersecurity · head to head

Proton Mail vs Sigstore

Proton Mail logo

Proton Mail

Cybersecurity

Secure email that protects your privacy

From
Free
Rated
-
Full reviewWebsite
Sigstore logo

Sigstore

Cybersecurity

Free public signing and transparency infrastructure for open source artifacts

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Proton Mail paid plan pricing not displayed on vendor site; Sigstore the security model depends on somebody watching the log. The documentation states that compromise of an identity provider or of Fulcio itself is detectable only if third parties monitor the transparency log, the monitoring tool is a community-tier rather than core project, and almost no consumer runs one.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Proton Mail and Sigstore actually diverge.

Attributes where Proton Mail and Sigstore differ
AttributeProton MailSigstore
Pricing modelfreemiumOpen source, public instance free to use
PlatformsWebWeb, Linux, macOS, Windows, Self-hosted

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Cybersecurity).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Proton Mail

Nothing recorded that Sigstore does not also cover.

Only in Sigstore

  • Fulcio
  • Rekor
  • Keyless signing
  • Multi-language clients
  • Timestamp authority
  • Neutral governance

What people use each for

The jobs each tool is most often brought in to do.

Proton Mail

  • Encrypted email communicationnot Sigstore
  • Privacy-focused email servicenot Sigstore
  • Family email protectionnot Sigstore

Sigstore

  • Open source projects signing releases without running a certificate authoritynot Proton Mail
  • Organisations meeting a signed-artifact requirement without buying a signing productnot Proton Mail
  • Publishing provenance that a consumer can verify independently of younot Proton Mail
  • Self-hosting the same components where a public log is unacceptablenot Proton Mail

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Proton Mail

  • Paid plan pricing not displayed on vendor site
  • Free tier limited to 1 GB storage
  • Free tier limited to single email address

Sigstore

  • The security model depends on somebody watching the log. The documentation states that compromise of an identity provider or of Fulcio itself is detectable only if third parties monitor the transparency log, the monitoring tool is a community-tier rather than core project, and almost no consumer runs one.
  • It is a 99.5 percent objective with no service level agreement, which permits several hours of downtime a month and offers no remedy. A pipeline that signs on every build has taken a hard dependency on a free service with no contract behind it.
  • Log scale is a live engineering problem rather than a theoretical one. The active shard holds billions of entries, the log has already been sharded twice, and sharding version 1 requires stopping traffic, which is why a replacement was built.
  • Ten-minute certificates make trust depend on log availability. Verifying an older signature relies on the log entry proving it was made inside that window, so a lost or unreachable entry can render a valid artifact unverifiable.
  • Migration debt is substantial and ongoing. Version 2 of the log is generally available but not the public default, the signing client has an announced breaking release ahead, some official clients lag the new log format, and a post-quantum migration is named as the next break after that.

Pricing, plan by plan

Proton Mail

Free

No published plan breakdown. See the Proton Mail review.

Sigstore

Free
  • Public good instanceFree
    • Free to everyone with no contract
    • 99.5 percent availability objective, not an agreement
    • 100KB cap per attestation upload
  • Self-hostedFree
    • Apache-2.0
    • Run your own Fulcio and Rekor
    • Rekor v2 available for self-hosters

Which should you pick?

Choose Proton Mail if

  • You want to start without paying.
Proton Mail review

Choose Sigstore if

  • You need fulcio.
  • You want to start without paying.
  • You work on Web, Linux, macOS, Windows, Self-hosted.
  • You also want rekor.
Sigstore review

Questions people ask

Is Proton Mail or Sigstore better?
Neither clearly leads. Proton Mail starts at Free and Sigstore at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Proton Mail or Sigstore?
Proton Mail starts at Free and Sigstore at Free.
Does Proton Mail or Sigstore run on more platforms?
Proton Mail runs on Web. Sigstore runs on Web, Linux, macOS, Windows, Self-hosted.
Can I use Proton Mail for free?
Both have a free tier, so you can try either at no cost before committing.
What is Proton Mail best used for?
Proton Mail is most often used for encrypted email communication, privacy-focused email service, family email protection. Of those, encrypted email communication and privacy-focused email service are not what Sigstore is typically brought in for.
What can Proton Mail do that Sigstore cannot?
Sigstore covers Fulcio, Rekor, Keyless signing, Multi-language clients.

Answered from the vendors’ own pages

Proton Mail: Is there a free version of Proton Mail?

Yes, Proton Mail offers a free plan with 1 GB storage, 1 encrypted email address, and basic features like folders, labels, and filters.

Source
Sigstore: Is the public instance really free?

Yes, with no contract and no paid tier. That is also the weakness: a 99.5 percent objective with no agreement, no remedy and support through Slack.

Proton Mail: What does the Mail Plus plan include?

Mail Plus includes 15 GB storage, 10 encrypted email addresses, support for 1 custom domain, 10 hide-my-email aliases, priority support, and access to Proton Calendar.

Source
Sigstore: Has the public log moved to Rekor v2?

No. Version 2 reached general availability in October 2025 and self-hosters can use it, but the public instance still defaults to version 1 and the project has said it will for the foreseeable future.

Proton Mail: What is included in Proton Unlimited?

Proton Unlimited provides 500 GB storage, 15 email addresses, 3 custom domains, unlimited hide-my-email aliases, access to Mail, Calendar, VPN, Drive, and Pass, plus dedicated support.

Source
Sigstore: Does Sigstore make my dependencies safe?

No, and this is a category error worth avoiding. It tells you who published something. It has no knowledge of what the artifact contains or whether it is vulnerable.

Proton Mail: Does Proton Mail offer a money-back guarantee?

Yes, Proton Mail provides a 30-day money-back guarantee for paid plans.

Source
Sigstore: What are the rate limits?

Not published. Only the 100KB cap per attestation upload is documented, so do not design a high-volume pipeline around assumed throughput.

Sigstore: Should we self-host it?

If a public record of every signature is unacceptable, or if a free service with no agreement cannot sit in your build path, then yes. Otherwise the public instance is what most projects use.

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