Glossary: Happ and Xray-core Terms

Every glossary page is built the same way: the essence of the term in the first paragraph, an example of how it appears in Happ, and the differences from similar terms at the end. You are not meant to read it from the start but by a specific word, from a link, an error, a setting or another article on the site.

For example, if you see flow=xtls-rprx-vision in a link, open the term XTLS Vision: it has a couple of paragraphs on what this mode is and which protocol it is meant for, without a breakdown of the whole link. If you need a breakdown of the whole link, go to a protocol page, for example VLESS in Happ.

The terms are combined into five groups by topic, not alphabetically:

Terms in one group usually link to each other: the page about Reality mentions VLESS, and the page about the routing profile mentions GeoIP and GeoSite. This way, after a few clicks, you get the full picture of a topic even without reading a wiki article.

A glossary term is a dictionary entry: a definition, one example and a list of differences. It does not explain why you need a whole subscription or how the routing profile and geo files relate to each other. A term is too narrow a format for that.

A wiki article solves a broader task. For example, “How Happ works” uses the terms TUN, system proxy and routing profile at the same time, shows how they are connected in one app, and explains why it is built that way. The general rule is simple: one word goes to the glossary, and a topic of several words and the links between them goes to the wiki.

Protocol terms in the glossary cover only the essence: what the protocol is, how it verifies the client, and what protects the channel. All the parameters of a specific link, such as the address, port and flags, are laid out separately in the protocols section, and a glossary term always points there at the end of its text.

Terms about the subscription and its parameters will be useful when reading the how-to guide “How to update a subscription”, where the same words appear in action rather than in a definition. And if you need to decide which protocol to choose, not just learn its essence, the VLESS vs VMess comparison, with a table of parameters, is closer to an answer than two separate terms.

The individual term pages are not available in English yet, so here are short definitions of the core terms.

• Xray-core — An open-source engine that implements the VLESS, VMess, Trojan, Shadowsocks and other proxy protocols, including their transports, TLS and routing. It is not an app or a service by itself: clients such as Happ embed it and add the interface and subscription handling.
• VLESS — A protocol for passing data between a client and an Xray-core server, in which the client presents a UUID and a destination address and the server forwards the traffic. It does not depend on the system clock, and in a typical setup the channel is protected by TLS or Reality.
• VMess — A proxy protocol from the V2Ray project that Xray-core supports for backward compatibility. The protocol encrypts the data itself, and the server separately checks a timestamp in each client request.
• Trojan — A proxy protocol that carries data inside an ordinary TLS connection and verifies the client by a password hash instead of a UUID. It has no encryption of its own, so it is not used without TLS.
• Shadowsocks — A proxy protocol with its own AEAD encryption and a shared secret between the client and the server. It needs no domain, certificate or TLS handshake, only an encryption method, a password or key, an address and a port.
• Hysteria2 — A proxy protocol over QUIC, a UDP-based transport with built-in TLS 1.3. It is designed for channels with high latency and packet loss and verifies the client by a password.
• Reality — A connection protection layer for VLESS in Xray-core. The server borrows the TLS handshake characteristics of a real website instead of using its own certificate, and the client verifies the server by an x25519 public key.
• TLS — The standard protocol for securing network connections. It verifies the server's identity by a certificate and encrypts data between the client and the server. It underlies the secure part of the web (HTTPS) and is one of the two protection layers for VLESS and Trojan in Xray-core.
• Subscription — An address from which Happ gets a list of server configurations and, optionally, service parameters such as a name, traffic and expiry date. Unlike a link to a single server, a subscription is stored in the app as a data source and is refreshed on a schedule or manually.
• Key / configuration link — The set of parameters for one server in Happ: protocol, address, port and sign-in data that the Xray-core engine uses to connect. It is added manually, by a protocol link or as part of a subscription, and then appears in the server list.
• Routing profile — A JSON set of settings attached to a Happ subscription. It defines the rules for directing traffic by domains and IP addresses, the DNS parameters, and links to the GeoIP and GeoSite files.
• GeoIP — The geoip.dat file with a database that groups IP address ranges by country and organization, so routing rules can refer to such a group with a single code instead of listing addresses.
• GeoSite — The geosite.dat file with a database that groups domains by category, so routing rules can refer to such a group with a single code instead of listing individual sites.
• TUN mode — A connection method in which the app creates a virtual network interface in the operating system and receives all of the device's traffic through it, not just the traffic of individual programs.
• System proxy — A connection mode in which Happ writes its local address and port into the operating system's proxy settings, rather than creating a separate network interface as in TUN mode.
• DNS-over-HTTPS — A protocol that sends a DNS query inside an ordinary HTTPS connection to a chosen server, instead of a separate unencrypted request on port 53, so it looks like a visit to an ordinary website.
• Ping — A way to check how many milliseconds a server takes to answer a request. In Happ it is available as an ICMP check, a TCP connection check, or a request through the proxy server itself to a target resource.
• Happ Crypt — The name of the family of algorithms that the Happ app uses to encrypt a subscription address before turning it into a happ://crypto link. The versions are numbered: crypt4 based on RSA-4096 and the newer crypt5 are documented.