Wire

Wire is a messenger for text, calls, video conferences and file sharing, built mainly for organisations: companies, government bodies and critical infrastructure operators. It is run by Wire Swiss GmbH in Zug, Switzerland, and was founded in 2012. Next to the paid team and enterprise plans Wire’s help centre lists a free personal plan, and its Google Play listing describes a free version for friends and family and for external business partners. According to the help centre, files on that plan can be up to 25 MB and are stored for one year.

Messages, calls and files in every conversation are end-to-end encrypted by default, with nothing to switch on, and this includes groups and channels. Files in Wire Drive, a feature of the team plans, are the exception. Wire is moving its conversations to Messaging Layer Security (MLS), an IETF standard, while conversations that have not moved yet still use Wire’s older Proteus protocol.

The trade-off is metadata. You sign up with a username and an email address instead of a phone number, but Wire’s servers keep the list of participants and devices in each conversation, and they know which accounts talk to which. The apps and the server are open source, yet Wire has published no audit of its MLS implementation.

Cryptography & Protocol

Wire’s standard messenger protocol is MLS, published by the IETF as RFC 9420 in July 2023. Wire says it was an initiator of MLS in 2016, and it describes its 2024 rollout as the first full MLS implementation in a mainstream messenger. The older protocol, Proteus, is Wire’s own implementation of the Double Ratchet algorithm, built on Curve25519, ChaCha20, HMAC-SHA256 and HKDF.

The move to MLS is still in progress. One-to-one conversations are being converted, and every new group or channel is created on MLS. A person whose devices do not support MLS yet cannot be added to a new group. To finish the migration, Wire asks users to make a backup, update every active device and remove inactive ones. In MLS conversations you can compare key fingerprints with the other person, but there is no button to mark a device as verified, as there was with Proteus.

Wire says it provides forward secrecy and post-compromise security: each message is encrypted with new keys, keys rotate during calls and after someone leaves a conversation, and old keys are deleted. The MLS standard itself names both properties for groups of two to thousands of members. Wire’s help article on the subject still describes the Proteus implementation.

End-to-end encryption is on by default for messages, one-to-one calls, conference calls and files, and it covers groups and channels as well. Calls run over SRTP with keys negotiated in a DTLS handshake, and conference calls use AES-GCM 256. Wire’s security whitepaper says the push notification services of Google and Apple receive only encrypted content.

The exception is Wire Drive, a file storage feature of the team plans. According to Wire, files and folders in Wire Drive are encrypted in transit and at rest, but not end-to-end. Messages and calls stay end-to-end encrypted there too.

Metadata Privacy

The sign-up identifier is an email address: Wire asks only for a username, an email address and a password, not a phone number. Contact discovery works by username or profile name. Other users cannot search for you by your email address or see it, and your profile name appears only to other Wire users who search for it, not on public search engines.

Wire’s servers delete an end-to-end encrypted message as soon as it is delivered. What they keep is the conversation itself: the list of participants and their devices, the conversation name, its creator, the creation time and the roles. Wire’s privacy whitepaper, dated July 2021, says this data is protected only by transport encryption between the app and the server. For each device the servers store its class, model, label and registration time, and the approximate location of the IP address used to register it. Technical logs are kept for up to 90 days.

Wire’s metadata protection stops at transport encryption: there is no sealed sender and no onion routing, so the servers know which accounts talk to which.

Telemetry is opt-in. The privacy policy says analytics data is processed only with your consent and deleted after 365 days at the latest.

Wire Swiss GmbH, which runs the service, is based in Zug, so Swiss law applies; the parent company, Wire Group Holdings GmbH, is incorporated in Berlin. Wire’s servers are in Germany and Ireland. The privacy policy says Wire discloses data to public authorities only where Swiss law requires it, and the transparency report says direct requests from foreign authorities cannot be granted. For 2025 the report counts 162 formally correct requests affecting 50 accounts, and 43 rejected requests. The report has no warrant canary.

Transparency & Verifiability

The Wire apps for Android, iPhone, desktop and the web are open source under the GPL-3.0 license, and so are the cryptography libraries. The server is open source under the AGPL-3.0 license. The server installs on Kubernetes, so organisations can run Wire on their own infrastructure: the service is self-hostable, while the public service runs on Wire’s own central servers.

Wire commissioned two public reviews from Kudelski Security and X41 D-Sec. The first, carried out between November 2016 and January 2017, covered the Proteus protocol and the Cryptobox library built on it. It made 14 findings, 9 low and 5 medium, none critical. The main one was that invalid public keys were processed without an error, which weakens recovery after a key compromise; the root cause was a bug in a third-party component. The second review, announced in March 2018, covered the Android and iOS apps, the web app and the signalling part of calls. Wire says all reported issues were fixed and the auditors reviewed the fixes.

Neither review covers the MLS implementation, which Wire introduced in 2024 and which every new group and channel now uses. Wire has published no newer audit report.

Wire holds ISO 27001 and ISO 27701 certification and Cyber Essentials certification. These certify how the company manages security and privacy, not the code of its apps.

Wire has no bug bounty. Vulnerabilities are reported by email, and Wire promises a first response within 2 business days. Reproducible builds are not documented, so you cannot check that the apps in the stores were built from the published code.

The 2021 account takeover vulnerability

In October 2021 the National Vulnerability Database (NVD) published CVE-2021-41093, a flaw in the Wire iOS app before version 3.86. An attacker who got hold of an old but still valid access token could take over the account by changing its email address. Version 3.86 fixed the flaw with a new endpoint that also requires an authentication cookie.

NVD gave the flaw a base score of 9.8, critical. GitHub, which reported it as the CVE numbering authority, scored it 7.4, high.

This was a vulnerability, not a leak of user data, so it does not count toward Wire’s data breach history.

Usability & Reach

Wire has apps for Android 8.0 and later, iPhone and iPad with iOS 17.0 and later, Windows 10 and later, and macOS 11.6 and later. The web app works in current Chrome, Edge and Firefox, but calls in the browser work only in Chrome 100 or later. Wire lists Linux builds for Ubuntu and as an AppImage, but marks them as community-supported and experimental.

Multi-device use does not depend on the phone: one account works on up to 8 devices, and each device has its own keys. On the web, one of the 8 can be a temporary device for a public computer. Because messages are encrypted separately for each device, a newly added device does not get the conversation history. The mobile app can hold up to 3 Wire accounts at once.

There is no cloud backup. The app exports the conversation history as a file that you store yourself, and a password for the file is optional. Wire warns that the backup file is not covered by its end-to-end encryption, and a backup cannot be restored if you forget its password.

Disappearing messages, which Wire calls self-deleting messages, are available, along with voice and video calls and video conferences; on the small-business plan conferences take up to 150 participants.

On Google Play, Wire has a rating of 3.2 from 36.8K reviews and 5M+ downloads.

Funding & Sustainability

Wire’s funding model is mixed. The company sells team and enterprise plans: the small-business plan costs €8.94 per person per month, or €7.45 with annual payment, and the enterprise plan is priced on request and adds federation and ID Shield, a device verification feature. Wire says more than 1,800 organisations use it.

The free tier is limited. According to the help centre, the personal plan allows files of up to 25 MB and keeps them for one year, while the paid plans allow 100 MB and keep files for good. A separate free team plan covers teams of up to five people.

Wire Group Holdings GmbH in Berlin is the parent company, and European institutional investors hold over 90% of it. The principal shareholders are Janus Friis, Cipio Partners, Schwarz Gruppe and Unternehmertum Venture Capital Partners. In 2019 a US holding company, Wire Holdings Inc. in Delaware, was set up for a funding round; it was unwound by August 2020. Benjamin Schilz has been CEO since January 2024.

Pros and Cons

• Messages, calls and files in every conversation, groups and channels included, are end-to-end encrypted by default (Wire Drive files excepted)
• MLS, an IETF standard, with forward secrecy and post-compromise security
• Sign-up needs a username and an email address, not a phone number, and nobody can find you by your email
• Delivered messages are deleted from the servers immediately
• One account works on up to 8 devices, each with its own keys and without depending on the phone
• The apps are open source under GPL-3.0 and the server under AGPL-3.0, and organisations can run their own server
• Kudelski Security and X41 D-Sec reviewed the Proteus protocol in 2016-2017 and the apps in 2018
• The service is run from Switzerland, with servers in Germany and Ireland and a yearly transparency report

• The servers keep the participants, devices and name of each conversation under transport encryption only
• No sealed sender or onion routing, so the servers know which accounts talk to which
• Wire has published no audit of its MLS implementation
• The move to MLS is unfinished, and MLS conversations have no button to verify a device
• Files in Wire Drive are encrypted in transit and at rest, not end-to-end
• New devices do not get the conversation history, and the only backup is a file outside Wire's end-to-end encryption
• The free personal plan limits files to 25 MB and keeps them for one year
• No bug bounty and no documented reproducible builds

Our Rating

• Cryptography & Protocol9.0/10

  Messages, calls and files in every conversation, groups and channels included, are end-to-end encrypted with nothing to switch on, and the MLS standard gives forward secrecy and post-compromise security. Migrated conversations use MLS while the rest still run on the older Proteus protocol, and files in Wire Drive are encrypted in transit and at rest, not end-to-end.

• Metadata Privacy6.0/10

  Sign-up needs a username and an email address, not a phone number, and nobody can find you by your email. The servers keep the participants, devices and name of each conversation under transport encryption only, and with no sealed sender or onion routing they know which accounts talk to which.

• Transparency & Verifiability7.5/10

  The apps are open source under GPL-3.0 and the server under AGPL-3.0, so anyone can run their own server, and Kudelski Security and X41 D-Sec reviewed the Proteus protocol and the apps. Wire has published no audit of its MLS implementation, has no bug bounty and does not document reproducible builds.

• Usability & Reach6.0/10

  Wire runs on Android, iPhone, Windows, Mac and the web, on up to 8 devices per account, with calls, conferences and self-deleting messages. New devices do not get the conversation history, the only backup is a file you save yourself, and the personal plan limits files to 25 MB and keeps them for one year.

• Funding & Sustainability7.5/10

  Paid team and enterprise plans used by more than 1,800 organisations, according to Wire, pay for the service, and European institutional investors hold over 90% of the company. The free personal plan has lower limits than the paid plans: 25 MB per file, and files kept for one year.

Overall7.4/10

Cryptography & Protocol 30% · Metadata Privacy 25% · Transparency & Verifiability 20% · Usability & Reach 15% · Funding & Sustainability 10%

See our rating methodology →