diff --git a/core.ts b/core.ts
index 39f3c58..d479da3 100644
--- a/core.ts
+++ b/core.ts
@@ -1,3 +1,5 @@
+import { isHex32 } from './utils.ts'
+
 export interface Nostr {
   generateSecretKey(): Uint8Array
   getPublicKey(secretKey: Uint8Array): string
@@ -36,7 +38,7 @@ export function validateEvent<T>(event: T): event is T & UnsignedEvent {
   if (typeof event.content !== 'string') return false
   if (typeof event.created_at !== 'number') return false
   if (typeof event.pubkey !== 'string') return false
-  if (!event.pubkey.match(/^[a-f0-9]{64}$/)) return false
+  if (!isHex32(event.pubkey)) return false
 
   if (!Array.isArray(event.tags)) return false
   for (let i = 0; i < event.tags.length; i++) {
diff --git a/nip10.ts b/nip10.ts
index d8b26d1..c19e7a8 100644
--- a/nip10.ts
+++ b/nip10.ts
@@ -1,7 +1,6 @@
 import type { Event } from './core.ts'
 import type { EventPointer, ProfilePointer } from './nip19.ts'
-
-const HEX64 = /^[0-9a-fA-F]{64}$/
+import { isHex32 } from './utils.ts'
 
 export function parse(event: Pick<Event, 'tags'>): {
   /**
@@ -43,7 +42,7 @@ export function parse(event: Pick<Event, 'tags'>): {
   for (let i = event.tags.length - 1; i >= 0; i--) {
     const tag = event.tags[i]
 
-    if (tag[0] === 'e' && tag[1] && HEX64.test(tag[1])) {
+    if (tag[0] === 'e' && tag[1] && isHex32(tag[1])) {
       const [_, eTagEventId, eTagRelayUrl, eTagMarker, eTagAuthor] = tag as [
         string,
         string,
@@ -55,7 +54,7 @@ export function parse(event: Pick<Event, 'tags'>): {
       const eventPointer: EventPointer = {
         id: eTagEventId,
         relays: eTagRelayUrl ? [eTagRelayUrl] : [],
-        author: eTagAuthor && HEX64.test(eTagAuthor) ? eTagAuthor : undefined,
+        author: eTagAuthor && isHex32(eTagAuthor) ? eTagAuthor : undefined,
       }
 
       if (eTagMarker === 'root') {
@@ -83,7 +82,7 @@ export function parse(event: Pick<Event, 'tags'>): {
       continue
     }
 
-    if (tag[0] === 'q' && tag[1] && HEX64.test(tag[1])) {
+    if (tag[0] === 'q' && tag[1] && isHex32(tag[1])) {
       const [_, eTagEventId, eTagRelayUrl] = tag as [string, string, undefined | string]
       result.quotes.push({
         id: eTagEventId,
@@ -91,7 +90,7 @@ export function parse(event: Pick<Event, 'tags'>): {
       })
     }
 
-    if (tag[0] === 'p' && tag[1] && HEX64.test(tag[1])) {
+    if (tag[0] === 'p' && tag[1] && isHex32(tag[1])) {
       result.profiles.push({
         pubkey: tag[1],
         relays: tag[2] ? [tag[2]] : [],
diff --git a/nip22.ts b/nip22.ts
index d2d8a76..c8149f6 100644
--- a/nip22.ts
+++ b/nip22.ts
@@ -1,7 +1,6 @@
 import type { Event } from './core.ts'
 import type { AddressPointer, EventPointer, ProfilePointer } from './nip19.ts'
-
-const HEX64 = /^[0-9a-fA-F]{64}$/
+import { isHex32 } from './utils.ts'
 
 export type ExternalPointer = {
   value: string
@@ -22,7 +21,7 @@ function parseAddressPointer(value: string, relayUrl?: string): AddressPointer |
   if (Number.isNaN(kind)) return undefined
 
   const pubkey = value.slice(idx + 1, idx2)
-  if (!HEX64.test(pubkey)) return undefined
+  if (!isHex32(pubkey)) return undefined
 
   return {
     kind,
@@ -36,11 +35,11 @@ function parsePointer(tag: string[]): EventPointer | AddressPointer | ExternalPo
   switch (tag[0]) {
     case 'E':
     case 'e':
-      if (!tag[1] || !HEX64.test(tag[1])) return undefined
+      if (!tag[1] || !isHex32(tag[1])) return undefined
       return {
         id: tag[1],
         relays: tag[2] ? [tag[2]] : [],
-        author: tag[3] && HEX64.test(tag[3]) ? tag[3] : undefined,
+        author: tag[3] && isHex32(tag[3]) ? tag[3] : undefined,
       }
     case 'A':
     case 'a':
@@ -63,12 +62,12 @@ function parseQuote(tag: string[]): EventPointer | AddressPointer | ExternalPoin
     return parseAddressPointer(tag[1], tag[2])
   }
 
-  if (!HEX64.test(tag[1])) return undefined
+  if (!isHex32(tag[1])) return undefined
 
   return {
     id: tag[1],
     relays: tag[2] ? [tag[2]] : [],
-    author: tag[3] && HEX64.test(tag[3]) ? tag[3] : undefined,
+    author: tag[3] && isHex32(tag[3]) ? tag[3] : undefined,
   }
 }
 
@@ -179,7 +178,7 @@ export function parse(event: Pick<Event, 'tags'>): {
       continue
     }
 
-    if ((tag[0] === 'P' || tag[0] === 'p') && tag[1] && HEX64.test(tag[1])) {
+    if ((tag[0] === 'P' || tag[0] === 'p') && tag[1] && isHex32(tag[1])) {
       result.profiles.push({
         pubkey: tag[1],
         relays: tag[2] ? [tag[2]] : [],
diff --git a/nip45.ts b/nip45.ts
index 4b441ed..fd3d421 100644
--- a/nip45.ts
+++ b/nip45.ts
@@ -3,6 +3,7 @@ import { bytesToHex } from '@noble/hashes/utils.js'
 
 import type { Event } from './core.ts'
 import type { Filter } from './filter.ts'
+import { isHex32 } from './utils.ts'
 
 const M = 256
 const HLL_HEX_LENGTH = M * 2
@@ -32,7 +33,7 @@ export function newHll(): Uint8Array {
 }
 
 export function hllDecode(hex: string): Uint8Array | undefined {
-  if (hex.length !== HLL_HEX_LENGTH || !/^[0-9a-fA-F]+$/.test(hex)) return undefined
+  if (hex.length !== HLL_HEX_LENGTH || !/^[0-9a-f]+$/.test(hex)) return undefined
 
   const registers = new Uint8Array(M)
   for (let i = 0; i < M; i++) {
@@ -54,9 +55,9 @@ export function hllEncode(registers: Uint8Array): string {
 export function computeOffset(filterFirstTagValue: string): number {
   let hex = filterFirstTagValue
 
-  if (!isHex64(hex)) {
+  if (!isHex32(hex)) {
     const parts = hex.split(':')
-    if (parts.length === 3 && isHex64(parts[1])) {
+    if (parts.length === 3 && isHex32(parts[1])) {
       hex = parts[1]
     } else {
       hex = bytesToHex(sha256(utf8Encoder.encode(filterFirstTagValue)))
@@ -79,7 +80,7 @@ export function getFilterFirstTagValue(filter: Filter): string | undefined {
 
 export function feedPubkey(hll: Uint8Array, pubkey: string, offset: number): Uint8Array {
   if (offset < 0 || offset > 24) throw new Error(`invalid offset ${offset}`)
-  if (!isHex64(pubkey)) throw new Error('pubkey must be 32-byte hex')
+  if (!isHex32(pubkey)) throw new Error('pubkey must be 32-byte hex')
 
   if (hll.length === 0) hll = newHll()
   if (hll.length !== M) throw new Error(`invalid number of registers ${hll.length}`)
@@ -123,10 +124,6 @@ export function estimateCount(hll: Uint8Array): number {
   return Math.floor(estimate)
 }
 
-function isHex64(value: string): boolean {
-  return /^[0-9a-fA-F]{64}$/.test(value)
-}
-
 function countLeadingZeroBitsAfterOffset(pubkey: string, offset: number): number {
   let zeroBits = 0
   for (let i = offset + 1; i < offset + 8; i++) {
diff --git a/nip57.ts b/nip57.ts
index cbedb0e..5d76521 100644
--- a/nip57.ts
+++ b/nip57.ts
@@ -1,7 +1,7 @@
 import { bech32 } from '@scure/base'
 
 import { NostrEvent, validateEvent, verifyEvent, type Event, type EventTemplate } from './pure.ts'
-import { utf8Decoder } from './utils.ts'
+import { isHex32, utf8Decoder } from './utils.ts'
 import { isReplaceableKind, isAddressableKind } from './kinds.ts'
 
 var _fetch: any
@@ -100,10 +100,10 @@ export function validateZapRequest(zapRequestString: string): string | null {
 
   let p = zapRequest.tags.find(([t, v]) => t === 'p' && v)
   if (!p) return "Zap request doesn't have a 'p' tag."
-  if (!p[1].match(/^[a-f0-9]{64}$/)) return "Zap request 'p' tag is not valid hex."
+  if (!isHex32(p[1])) return "Zap request 'p' tag is not valid hex."
 
   let e = zapRequest.tags.find(([t, v]) => t === 'e' && v)
-  if (e && !e[1].match(/^[a-f0-9]{64}$/)) return "Zap request 'e' tag is not valid hex."
+  if (e && !isHex32(e[1])) return "Zap request 'e' tag is not valid hex."
 
   let relays = zapRequest.tags.find(([t, v]) => t === 'relays' && v)
   if (!relays) return "Zap request doesn't have a 'relays' tag."
diff --git a/nipb0.ts b/nipb0.ts
index 19be7a7..036c47a 100644
--- a/nipb0.ts
+++ b/nipb0.ts
@@ -3,6 +3,7 @@ import { bytesToHex } from '@noble/hashes/utils.js'
 import type { EventTemplate } from './core.ts'
 import type { Signer } from './signer.ts'
 import { kinds } from './index.ts'
+import { isHex32 } from './utils.ts'
 
 export type BlobDescriptor = {
   url: string
@@ -27,10 +28,6 @@ export type AuthEventOptions = {
   expiration?: number
 }
 
-export function isSha256(str: string): boolean {
-  return /^[0-9a-f]{64}$/i.test(str)
-}
-
 export function getBlobSize(blob: UploadType): number {
   if ((typeof File !== 'undefined' && blob instanceof File) || blob instanceof Blob) {
     return blob.size
@@ -213,7 +210,7 @@ export function parseBlossomURI(uri: string): BlossomURI {
   if (dotIndex === -1) throw new Error('Invalid blossom URI: missing file extension')
   const sha256 = path.slice(0, dotIndex)
   const ext = path.slice(dotIndex + 1)
-  if (!isSha256(sha256)) throw new Error('Invalid blossom URI: invalid sha256 hash')
+  if (!isHex32(sha256)) throw new Error('Invalid blossom URI: invalid sha256 hash')
   if (!ext) throw new Error('Invalid blossom URI: empty file extension')
   const params = new URLSearchParams(query)
   const servers = params.getAll('xs')
@@ -250,7 +247,7 @@ export function blossomURIFromURL(url: URL): BlossomURI {
   if (dotIndex === -1) throw new Error('Invalid blossom URL: missing file extension')
   const sha256 = path.slice(0, dotIndex)
   const ext = path.slice(dotIndex + 1)
-  if (!isSha256(sha256)) throw new Error('Invalid blossom URL: invalid sha256 hash')
+  if (!isHex32(sha256)) throw new Error('Invalid blossom URL: invalid sha256 hash')
   if (!ext) throw new Error('Invalid blossom URL: empty file extension')
   const servers = url.searchParams.getAll('xs')
   const authors = url.searchParams.getAll('as')
@@ -743,7 +740,7 @@ export class BlossomClient {
   }
 
   async check(hash: string): Promise<void> {
-    if (!isSha256(hash)) throw new Error(`${hash} is not valid 32-byte hex`)
+    if (!isHex32(hash)) throw new Error(`${hash} is not valid 32-byte hex`)
     await this.httpCall('HEAD', hash)
   }
 
diff --git a/nipb7.ts b/nipb7.ts
index 94b57de..5753f46 100644
--- a/nipb7.ts
+++ b/nipb7.ts
@@ -1,7 +1,7 @@
 import { sha256 } from '@noble/hashes/sha2.js'
 import { EventTemplate } from './core.ts'
 import { Signer } from './signer.ts'
-import { bytesToHex } from './utils.ts'
+import { bytesToHex, isHex32 } from './utils.ts'
 
 export type BlobDescriptor = {
   url: string
@@ -84,12 +84,8 @@ export class BlossomClient {
     }
   }
 
-  private isValid32ByteHex(hash: string): boolean {
-    return /^[a-f0-9]{64}$/i.test(hash)
-  }
-
   async check(hash: string): Promise<void> {
-    if (!this.isValid32ByteHex(hash)) {
+    if (!isHex32(hash)) {
       throw new Error(`${hash} is not a valid 32-byte hex string`)
     }
 
@@ -125,7 +121,7 @@ export class BlossomClient {
   }
 
   async download(hash: string): Promise<ArrayBuffer> {
-    if (!this.isValid32ByteHex(hash)) {
+    if (!isHex32(hash)) {
       throw new Error(`${hash} is not a valid 32-byte hex string`)
     }
 
@@ -156,7 +152,7 @@ export class BlossomClient {
   async list(): Promise<BlobDescriptor[]> {
     const pubkey = await this.signer.getPublicKey()
 
-    if (!this.isValid32ByteHex(pubkey)) {
+    if (!isHex32(pubkey)) {
       throw new Error(`pubkey ${pubkey} is not valid`)
     }
 
@@ -179,7 +175,7 @@ export class BlossomClient {
   }
 
   async delete(hash: string): Promise<void> {
-    if (!this.isValid32ByteHex(hash)) {
+    if (!isHex32(hash)) {
       throw new Error(`${hash} is not a valid 32-byte hex string`)
     }
 
diff --git a/utils.ts b/utils.ts
index a6031f8..59a8dec 100644
--- a/utils.ts
+++ b/utils.ts
@@ -123,3 +123,16 @@ export function mergeReverseSortedLists(list1: NostrEvent[], list2: NostrEvent[]
 
   return result
 }
+
+/**
+ * Checks if a string is a 64-char lowercase hex string as most Nostr ids and pubkeys.
+ */
+export function isHex32(input: string): boolean {
+  for (let i = 0; i < 64; i++) {
+    let cc = input.charCodeAt(i)
+    if (isNaN(cc) || cc < 48 || cc > 102 || (cc > 57 && cc < 97)) {
+      return false
+    }
+  }
+  return true
+}