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Velt
Standard library · 62 modules

Batteries included, written in Velt.

Import a module by its path, velt/<area>/<module>. It is Velt code, specialized and inlined into your program like your own, so you only pay for what you use. The overview has the conventions they share.

import { readFile } from "velt/fs";
import { Deque } from "velt/collections";

Web & network

Clients, sockets, wire formats
velt/net/httpfetch, Request, Response and Headers: globals, as in Node.18 exports · 83% documentedvelt/net/http/h2HTTP/2's frames and HPACK, for clients and servers.55 exports · 100% documentedvelt/net/websocketWebSocket clients, and sockets over an upgraded connection.8 exports · 88% documentedvelt/netTCP and TLS: listen, connect, streams.9 exports · 78% documentedvelt/net/udpUDP sockets and datagrams.3 exports · 100% documentedvelt/net/dnsHost name resolution through the system resolver.2 exports · 100% documentedvelt/net/urlWHATWG URL, URLSearchParams and URI encoding.7 exports · 100% documented

Data & formats

Rows, JSON, CSV
velt/dbTyped rows from any row source, for database drivers.8 exports · 100% documentedvelt/encoding/jsonJSON values. JSON.parse<T> is built in.6 exports · 100% documentedvelt/encoding/csvRFC 4180 parse and stringify.6 exports · 100% documentedvelt/encodingBase64, hex and UTF-8.21 exports · 100% documentedvelt/compressgzip, zlib, DEFLATE and Brotli decompression.9 exports · 100% documented

Files & processes

The machine you run on
velt/fsAsync and sync file system API.48 exports · 100% documentedFile streamsChunked and line readers, buffered writers.velt/ioIoError, the error the I/O modules share.8 exports · 100% documentedvelt/pathjoin, dirname, basename, normalize.8 exports · 100% documentedvelt/processargv, env, cwd, exit, stdout.22 exports · 100% documentedvelt/process: stdinreadLine, lines and readAll.velt/process/childexec, spawn and ChildProcess.9 exports · 100% documentedvelt/osplatform, arch, availableParallelism, tmpdir.6 exports · 100% documentedvelt/cliArgParser: flags, options, positionals and help text.5 exports · 100% documented

Concurrency

Tasks across every core
velt/taskCancellation, timeouts and taskScope.11 exports · 100% documentedvelt/syncAtomic building blocks: Backoff and VersionLatch.7 exports · 100% documentedvelt/sync: channelsTyped queues between tasks.velt/sync/epochEpoch-based reclamation of shared values.7 exports · 100% documentedvelt/time: timerssetTimeout, setInterval, delay and Ticker.

Security & randomness

Hashes, keys, ids
velt/cryptoSHA-256, SHA-1, HMAC, randomBytes, timingSafeEqual.10 exports · 100% documentedvelt/hashfnv1a64: a stable, non-cryptographic hash.2 exports · 100% documentedvelt/randomFast random numbers, not for secrets.2 exports · 100% documentedvelt/random/uuiduuidv4, uuidv7, parse and validate.8 exports · 100% documented

Text, time & HTML

Strings people read
velt/textRegular expressions, StringBuilder and HTML escaping.6 exports · 100% documentedvelt/text: RegExpRegExp on a linear-time engine.velt/text: StringBuilderBuilds a string in one growing buffer.velt/text: escapeHtmlescapeHtml in one pass.velt/timeDateTime, Duration, timers, delay and Ticker.14 exports · 100% documentedvelt/time: DateTimeUTC-first DateTime and Duration.velt/jsxServer-side TSX: renderToString and streaming.13 exports · 100% documentedvelt/jsx/attrsThe attribute types of the HTML, SVG and MathML elements.80 exports · 100% documentedvelt/jsx/jsx-runtimeThe JSX provider module compiled TSX calls, and the generic one.19 exports · 100% documented

Collections & memory

Beyond Array and Map
velt/collectionsDeque, PriorityQueue, SortedMap, BTreeMap, ConcurrentMap, Set.8 exports · 100% documentedSetSet with ES2025 set algebra.DequeRing-buffer double-ended queue.PriorityQueueBinary heap ordered by a comparator.SortedMapKey-ordered map on two sorted arrays.BTreeMapKey-ordered B+tree map for large maps.ConcurrentMapA map many threads read and write at once.velt/memneedsDrop and Blank, for containers.3 exports · 100% documentedArenaA typed memory pool (a region).velt/mathgcd, lcm, clamp and other integer helpers.7 exports · 100% documentedBigIntArbitrary-precision integers.velt/simdVector types and lane-wise methods.14 exports · 0% documented

Tests & tooling

For libraries and tools
velt/testThe runner velt test builds into test programs.10 exports · 100% documentedvelt/test/httpexpect matchers for a Response.velt/packageThe type of the package manifest, package.vlt.7 exports · 100% documentedvelt/devThe graceful stop under velt dev.2 exports · 100% documentedvelt/generateWhat source generators are written with.11 exports · 100% documentedvelt/nativeThe Velt side of packages with native code.6 exports · 100% documentedvelt/reflectWhat an any holds at run time.12 exports · 100% documented

Built-ins

In scope everywhere, no import
PreludeStrings, arrays, Map, Math, JSON, Error, promises.StreamsReadableStream and its reader and controller.The prelude: typed arraysArrayBuffer, DataView and the typed arrays.11 exports · 100% documentedThe prelude: SymbolUnique values compared by identity.2 exports · 100% documented

Packages

Servers and database drivers are libraries, not std
http-serverAn HTTP/1.1 and HTTP/2 server with web-standard Request and Response handlers.sqliteEmbedded SQLite close to better-sqlite3, and an engine written in Velt.postgresA PostgreSQL client close to node-postgres.redisA Redis client close to ioredis: pipelines, transactions, pub/sub.
Need something that isn't here yet?A Velt package can include any Rust crate and export its functions with #[export]. Your users never need Rust.
Native packages →