@atproto/common-web - AT Protocol

The @atproto/common-web package provides shared utilities and helper functions used across AT Protocol packages. All utilities are web-platform-friendly and work in browsers, Node.js, and other JavaScript runtimes.

Installation

npm install @atproto/common-web

Overview

This package contains:

TID - Timestamp Identifiers for distributed systems
Async utilities - Promise helpers and async iteration
Data structures - Array and object manipulation
DID Document utilities - Working with DID documents
IPLD utilities - Content addressing and encoding
Retry logic - Configurable retry mechanisms
Time utilities - Time parsing and formatting
String utilities - String manipulation helpers

This package is designed to be a dependency of other @atproto/* packages. Most applications should use @atproto/api instead of importing this package directly.

TID (Timestamp Identifier)

TIDs are time-ordered identifiers used throughout AT Protocol for records, events, and other entities.

Class: TID

import { TID } from '@atproto/common-web'

TID.next

(prev?: TID) => TID

Generate the next TID

const tid = TID.next()
console.log(tid.toString()) // "3l4yhqsgvzc2g"

TID.nextStr

(prev?: string) => string

Generate the next TID as a string

const tidStr = TID.nextStr()

TID.fromTime

(timestamp: number, clockid: number) => TID

Create a TID from a timestamp and clock ID

const tid = TID.fromTime(Date.now() * 1000, 0)

TID.fromStr

(str: string) => TID

Parse a TID from a string

const tid = TID.fromStr('3l4yhqsgvzc2g')

TID.is

(str: string) => boolean

Check if a string is a valid TID

if (TID.is(str)) {
  // Valid TID
}

Instance Methods

const tid = TID.next()

// Get timestamp (microseconds since epoch)
const timestamp = tid.timestamp()

// Get clock ID
const clockid = tid.clockid()

// Format with dashes
const formatted = tid.formatted() // "3l4y-hqs-gvzc-2g"

// Convert to string
const str = tid.toString() // "3l4yhqsgvzc2g"

// Compare TIDs
const other = TID.next()
const comparison = tid.compareTo(other) // -1, 0, or 1
const isNewer = tid.newerThan(other)
const isOlder = tid.olderThan(other)
const isEqual = tid.equals(other)

Sorting

const tids = [tid3, tid1, tid2]

// Sort oldest first
tids.sort(TID.oldestFirst)

// Sort newest first
tids.sort(TID.newestFirst)

Async Utilities

retry

Retry a function with exponential backoff:

import { retry } from '@atproto/common-web'

const result = await retry(
  async () => {
    return await fetchData()
  },
  {
    maxRetries: 3,
    initialDelay: 100,
    maxDelay: 1000,
    retryable: (error) => error.status === 429,
  }
)

() => Promise<T>

required

The async function to retry

options.maxRetries

number

Maximum number of retry attempts (default: 3)

options.initialDelay

number

Initial delay in milliseconds (default: 100)

options.maxDelay

number

Maximum delay in milliseconds (default: 5000)

options.retryable

(error: unknown) => boolean

Function to determine if an error is retryable (default: all errors retryable)

wait

Delay execution for a specified time:

import { wait } from '@atproto/common-web'

await wait(1000) // Wait 1 second

bailableWait

Create a wait that can be cancelled:

import { bailableWait } from '@atproto/common-web'

const { wait, bail } = bailableWait(5000)

// In one path
wait().then(() => console.log('Waited 5 seconds'))

// In another path, cancel early
setTimeout(() => bail(), 1000)

Array Utilities

chunkArray

Split an array into chunks:

import { chunkArray } from '@atproto/common-web'

const items = [1, 2, 3, 4, 5, 6, 7]
const chunks = chunkArray(items, 3)
// [[1, 2, 3], [4, 5, 6], [7]]

dedupeStrs

Remove duplicate strings from an array:

import { dedupeStrs } from '@atproto/common-web'

const unique = dedupeStrs(['a', 'b', 'a', 'c', 'b'])
// ['a', 'b', 'c']

range

Create an array of numbers:

import { range } from '@atproto/common-web'

const numbers = range(5)
// [0, 1, 2, 3, 4]

asyncFilter

Filter array with async predicate:

import { asyncFilter } from '@atproto/common-web'

const results = await asyncFilter(items, async (item) => {
  return await checkItem(item)
})

Object Utilities

omit

Create a shallow copy without specified keys:

import { omit } from '@atproto/common-web'

const obj = { a: 1, b: 2, c: 3 }
const result = omit(obj, ['b'])
// { a: 1, c: 3 }

noUndefinedVals

Remove undefined values from an object:

import { noUndefinedVals } from '@atproto/common-web'

const obj = { a: 1, b: undefined, c: 3 }
const result = noUndefinedVals(obj)
// { a: 1, c: 3 }

String Utilities

parseLanguage

Parse a language code:

import { parseLanguage } from '@atproto/common-web'

const lang = parseLanguage('en-US')
// { language: 'en', region: 'US' }

s32encode / s32decode

Encode/decode numbers using base-32 (sortable variant):

import { s32encode, s32decode } from '@atproto/common-web'

const encoded = s32encode(12345)
const decoded = s32decode(encoded)

DID Document Utilities

isValidDidDoc

Validate a DID document structure:

import { isValidDidDoc } from '@atproto/common-web'

if (isValidDidDoc(doc)) {
  // Valid DID document
}

getPdsEndpoint

Extract the PDS endpoint from a DID document:

import { getPdsEndpoint } from '@atproto/common-web'

const endpoint = getPdsEndpoint(didDoc)
// "https://pds.example.com"

getEntryUrlFromDidDoc

Get the entry URL for a service:

import { getEntryUrlFromDidDoc } from '@atproto/common-web'

const url = getEntryUrlFromDidDoc(
  didDoc,
  'did:web:example.com',
  'AtprotoPersonalDataServer'
)

IPLD Utilities

cidForCbor

Generate a CID for CBOR data:

import { cidForCbor } from '@atproto/common-web'

const data = { hello: 'world' }
const cid = await cidForCbor(data)

verifyCidForBytes

Verify that bytes match a CID:

import { verifyCidForBytes } from '@atproto/common-web'

const isValid = await verifyCidForBytes(
  cid,
  bytes
)

Type Guards

check

The check namespace provides type checking utilities:

import { check } from '@atproto/common-web'

// Check if value is defined
if (check.is(value)) {
  // value is not null or undefined
}

Error Utilities

aggregateErrors

Combine multiple errors:

import { aggregateErrors } from '@atproto/common-web'

const errors = [error1, error2, error3]
const combined = aggregateErrors(errors, 'Multiple operations failed')

throw combined

isErrnoException

Check if error is a Node.js errno exception:

import { isErrnoException } from '@atproto/common-web'

if (isErrnoException(error)) {
  console.log('Error code:', error.code)
}

errHasMsg

Check if error has a specific message:

import { errHasMsg } from '@atproto/common-web'

if (errHasMsg(error, 'ENOENT')) {
  // Handle file not found
}

Binary Data Utilities

flattenUint8Arrays

Combine multiple Uint8Arrays:

import { flattenUint8Arrays } from '@atproto/common-web'

const arrays = [new Uint8Array([1, 2]), new Uint8Array([3, 4])]
const flattened = flattenUint8Arrays(arrays)
// Uint8Array([1, 2, 3, 4])

streamToBuffer

Convert async iterable to Uint8Array:

import { streamToBuffer } from '@atproto/common-web'

async function* generateChunks() {
  yield new Uint8Array([1, 2])
  yield new Uint8Array([3, 4])
}

const buffer = await streamToBuffer(generateChunks())
// Uint8Array([1, 2, 3, 4])

Time Utilities

parseIntWithFallback

Parse integer with fallback:

import { parseIntWithFallback } from '@atproto/common-web'

const value = parseIntWithFallback('123', 0) // 123
const invalid = parseIntWithFallback('abc', 0) // 0

jitter

Generate random jitter:

import { jitter } from '@atproto/common-web'

const delay = 1000 + jitter(200)
// Random value between 800 and 1200

Complete Examples

Retry with Custom Logic

import { retry, wait } from '@atproto/common-web'

interface ApiError {
  status: number
  retryAfter?: number
}

async function fetchWithRetry(url: string) {
  return retry(
    async () => {
      const response = await fetch(url)
      if (!response.ok) {
        const error: ApiError = {
          status: response.status,
          retryAfter: parseInt(response.headers.get('Retry-After') || '0'),
        }
        throw error
      }
      return response.json()
    },
    {
      maxRetries: 5,
      retryable: (error: any) => {
        // Retry on 429 (rate limit) and 5xx errors
        return error.status === 429 || error.status >= 500
      },
    }
  )
}

Batch Processing with Chunks

import { chunkArray, wait } from '@atproto/common-web'

async function processBatch(items: string[]) {
  const chunks = chunkArray(items, 10)
  
  for (const chunk of chunks) {
    await Promise.all(
      chunk.map(item => processItem(item))
    )
    
    // Rate limiting
    await wait(100)
  }
}

async function processItem(item: string) {
  console.log('Processing:', item)
  // Process the item
}

Working with TIDs

import { TID } from '@atproto/common-web'

class RecordManager {
  private lastTid?: TID
  
  createRecord(data: any) {
    const tid = TID.next(this.lastTid)
    this.lastTid = tid
    
    return {
      rkey: tid.toString(),
      data,
      createdAt: new Date(tid.timestamp() / 1000),
    }
  }
  
  isRecordNewer(tid1: string, tid2: string): boolean {
    return TID.fromStr(tid1).newerThan(TID.fromStr(tid2))
  }
  
  sortRecords(records: { rkey: string }[]) {
    return records.sort((a, b) => {
      return TID.fromStr(a.rkey).compareTo(TID.fromStr(b.rkey))
    })
  }
}

Stream Processing

import { streamToBuffer, flattenUint8Arrays } from '@atproto/common-web'

async function downloadFile(url: string): Promise<Uint8Array> {
  const response = await fetch(url)
  
  if (!response.body) {
    throw new Error('No response body')
  }
  
  // Convert ReadableStream to AsyncIterable
  const reader = response.body.getReader()
  
  async function* stream() {
    try {
      while (true) {
        const { done, value } = await reader.read()
        if (done) break
        yield value
      }
    } finally {
      reader.releaseLock()
    }
  }
  
  return streamToBuffer(stream())
}

Type Definitions

Key types exported from the package:

// Utility types
export type DateISO = string
export type TimeISO = string

// Error types
export interface ErrnoException extends Error {
  errno?: number
  code?: string
  path?: string
  syscall?: string
}

// Async types
export interface RetryOptions {
  maxRetries?: number
  initialDelay?: number
  maxDelay?: number
  retryable?: (error: unknown) => boolean
}

export interface BailableWait {
  bail: () => void
  wait: () => Promise<void>
}

@atproto/api - High-level AT Protocol client
@atproto/xrpc - XRPC client library
@atproto/syntax - AT Protocol syntax utilities
@atproto/lexicon - Lexicon schema validation

Notes

All utilities are designed to work in web browsers and Node.js
The package has no platform-specific dependencies
TID generation is not cryptographically secure but provides collision resistance
Retry logic uses exponential backoff with jitter

Client Libraries

Core Packages

OAuth

Server

Documentation Index

​Installation

​Overview

​TID (Timestamp Identifier)

​Class: TID

​Instance Methods

​Sorting

​Async Utilities

​retry

​wait

​bailableWait

​Array Utilities

​chunkArray

​dedupeStrs

​range

​asyncFilter

​Object Utilities

​omit

​noUndefinedVals

​String Utilities

​parseLanguage

​s32encode / s32decode

​DID Document Utilities

​isValidDidDoc

​getPdsEndpoint

​getEntryUrlFromDidDoc

​IPLD Utilities

​cidForCbor

​verifyCidForBytes

​Type Guards

​check

​Error Utilities

​aggregateErrors

​isErrnoException

​errHasMsg

​Binary Data Utilities

​flattenUint8Arrays

​streamToBuffer

​Time Utilities

​parseIntWithFallback

​jitter

​Complete Examples

​Retry with Custom Logic

​Batch Processing with Chunks

​Working with TIDs

​Stream Processing

​Type Definitions

​Related Packages

​Notes

​See Also

Build docs developers (and LLMs) love

Installation

Overview

TID (Timestamp Identifier)

Class: TID

Instance Methods

Sorting

Async Utilities

retry

wait

bailableWait

Array Utilities

chunkArray

dedupeStrs

range

asyncFilter

Object Utilities

omit

noUndefinedVals

String Utilities

parseLanguage

s32encode / s32decode

DID Document Utilities

isValidDidDoc

getPdsEndpoint

getEntryUrlFromDidDoc

IPLD Utilities

cidForCbor

verifyCidForBytes

Type Guards

check

Error Utilities

aggregateErrors

isErrnoException

errHasMsg

Binary Data Utilities

flattenUint8Arrays

streamToBuffer

Time Utilities

parseIntWithFallback

jitter

Complete Examples

Retry with Custom Logic

Batch Processing with Chunks

Working with TIDs

Stream Processing

Type Definitions

Related Packages

Notes

See Also