--- title: "Polkadot App Reference" description: "Reference for the Polkadot App, the mobile Host in the Triangle that holds the user's signing key, runs PoP, and approves every Product transaction." categories: "Apps, Reference" url: "https://developers.polkadot.com/reference/apps/hosts/polkadot-app/" word_count: 696 token_estimate: 1079 version_hash: "sha256:8998c843e8063c3ea0f142d2184eee57012295ea07d0d6f956587dfcbe931eb2" last_updated: "2026-11-13T11:04:04+00:00" --- # Polkadot App ## Introduction The Polkadot App is the mobile wallet that holds every Polkadot Product user's private key. It runs on the user's phone and is the only place in the [Polkadot Triangle](/reference/glossary/#triangle) where the key lives — [Polkadot Desktop](/reference/apps/hosts/polkadot-desktop/) and [Polkadot Web](/reference/apps/hosts/polkadot-web/) never touch it. From a Product developer's perspective, the App plays three roles no other Host plays: - **It holds the user's private key**: The key lives on the device, in the App's on-device storage. No other Host and no Product ever sees the key. - **It signs every transaction**: Every signing request that originates from a Product — whether the Product runs inside Desktop or Web — is routed back to the App for the user to approve on their phone. - **It runs Proof of Personhood**: [Proof of Personhood](/reference/apps/hosts/polkadot-app/pop/) is the privacy-preserving "real human" check that unlocks alias-gated features. The verification happens inside the App; the Product never sees who the user is. The App also exposes two groups of features that Products integrate against: - **Host-level features**: [Chat](/reference/apps/hosts/polkadot-app/chat/) is the messaging surface that pairs the [Statement Store](/reference/apps/infrastructure/statement-store/) and [Bulletin Chain](/reference/apps/infrastructure/bulletin-chain/). [Sign In with Polkadot](/reference/apps/hosts/polkadot-app/sign-in/) is the cross-Host authentication handshake initiated by Desktop or Web. - **Payment-side features**: [Coinage](/reference/apps/hosts/polkadot-app/coinage/) is the peer-to-peer payment flow. [Pocket](/reference/apps/hosts/polkadot-app/pocket/) is the App-side recipient counterpart to Desktop's Pocket send flow. ## How It Works From a Product developer's perspective, three things matter about how the App runs: - **Session pairing**: Pairing establishes a session, not a copy of the key. When the user pairs the App with Polkadot Desktop, the App returns a derived _session public key_ (see [Install Desktop and Pair](/apps/get-started/)). Desktop stores that public key so it can identify the user and construct per-Product sub-accounts. The private key never leaves the phone. - **Asynchronous signing**: Signing is asynchronous because it happens on a separate device. When a Product calls `signAndSubmit`, Desktop renders a signing modal locally, but the actual signature happens on the user's phone after they approve in the App. Build UI that tolerates the round-trip; see the [Sign and Submit Transactions](/apps/build/sign-and-submit/) guide for the patterns. - **PoP verification**: The App is the only place PoP runs. A Product can gate features on Proof of Personhood (alias-based or general personhood), but the verification flow itself happens in the App. The Product never sees the underlying biometric or the user's identity record, only the alias or alias-proof it requested through TrUAPI. ## Where the App Fits in the SDK Surface The App is both a consumer and a producer of [TrUAPI](/reference/apps/protocol/truapi/) methods: - The App consumes Host API methods for chain interaction and storage when its own features (Chat, Coinage, PoP) need to talk to the People Chain, Statement Store, or Bulletin Chain. - The App produces the signing primitive every other Host's `signAndSubmit` ultimately resolves against. Methods Products call through the SDK — like `createProof` and `getAnonymousAlias` — complete in the App on the user's phone. ## Where to Go Next
- **Chat** --- The in-App messaging surface: room/bot registration, the typed-message system, and how Chat composes the Statement Store with the Bulletin Chain. [→ Reference](/reference/apps/hosts/polkadot-app/chat/) - **Proof of Personhood** --- Where the App's PoP verification happens, what Ring-VRF aliases are, and the PoP Full vs PoP Lite tier model. [→ Reference](/reference/apps/hosts/polkadot-app/pop/) - **Sign In with Polkadot** --- The Host-level handshake the App resolves when Desktop or Web wants to authenticate a session against the paired identity. [→ Reference](/reference/apps/hosts/polkadot-app/sign-in/) - **Accounts and Signing** --- The how-to guide for wiring a Product up to a paired account and submitting signed transactions through the SDK. [→ Get Started](/apps/build/sign-and-submit/)