Make the Esplora API base URL configurable

Hardcoded MEMPOOL_API constant in src/lib/bitcoin.ts becomes a baseUrl
parameter on every fetch helper, sourced from a new `esploraBaseUrl`
field on AppConfig (default `https://mempool.space/api`). The wallet,
zap dialogs, on-chain zap verification, and NIP-73 Bitcoin tx/address
pages now read the URL from useAppContext and pass it through, so
self-hosted Esplora deployments (or Blockstream's) work without code
changes. The mempool.space-specific `/v1/prices` extension is still
appended by fetchBtcPrice.

WALLET.md

@@ -91,15 +91,15 @@ bitcoin.initEccLib(ecc);
 
 ## Balance & Transaction APIs
 
-All Bitcoin data is fetched from the public [mempool.space](https://mempool.space) Esplora-compatible API:
+All Bitcoin data is fetched from an [Esplora](https://github.com/Blockstream/esplora/blob/master/API.md)-compatible REST API. The base URL is read from `AppConfig.esploraBaseUrl` (default: `https://mempool.space/api`) and can be overridden in `ditto.json` at build time or in Settings at runtime. Any Esplora-compatible backend works (mempool.space, Blockstream, self-hosted).
 
-| Endpoint | Purpose |
+| Endpoint (relative to `esploraBaseUrl`) | Purpose |
 |---|---|
-| `GET https://mempool.space/api/address/{address}` | Balance stats (funded/spent sums, tx counts) |
-| `GET https://mempool.space/api/address/{address}/txs` | Transaction history for an address |
-| `GET https://mempool.space/api/tx/{txid}` | Full transaction detail (inputs, outputs, fee, block) |
+| `GET /address/{address}` | Balance stats (funded/spent sums, tx counts) |
+| `GET /address/{address}/txs` | Transaction history for an address |
+| `GET /tx/{txid}` | Full transaction detail (inputs, outputs, fee, block) |
 
-The wallet page polls balance and transaction data every 30 seconds. BTC/USD price is fetched from mempool.space every 60 seconds.
+The wallet page polls balance and transaction data every 30 seconds. BTC/USD price is fetched every 60 seconds via `GET /v1/prices` — a mempool.space-specific extension that is not part of the standard Esplora REST surface.
 
 ## NIP-73 Integration
 
@@ -140,9 +140,9 @@ The signer classes (`NSecSignerBtc`, `NBrowserSignerBtc`, `NConnectSignerBtc`) e
 
 The send flow constructs a standard Taproot (P2TR) key-path spend:
 
-1. **Fetch UTXOs** -- All unspent outputs for the sender's address are retrieved from `mempool.space/api/address/{address}/utxo`.
+1. **Fetch UTXOs** -- All unspent outputs for the sender's address are retrieved from `GET {esploraBaseUrl}/address/{address}/utxo`.
 
-2. **Fetch fee rates** -- Recommended fee rates (sat/vB) for four confirmation targets are retrieved from `mempool.space/api/fee-estimates`:
+2. **Fetch fee rates** -- Recommended fee rates (sat/vB) for four confirmation targets are retrieved from `GET {esploraBaseUrl}/fee-estimates`:
 
    | Speed | Block target | Typical wait |
    |---|---|---|
@@ -170,7 +170,7 @@ The send flow constructs a standard Taproot (P2TR) key-path spend:
 
    For extension and bunker signers, the tweaking is handled by the external signer.
 
-8. **Finalize and broadcast** -- The signed PSBT is finalized, the raw transaction hex is extracted, and POSTed to `mempool.space/api/tx`, which returns the txid on success.
+8. **Finalize and broadcast** -- The signed PSBT is finalized, the raw transaction hex is extracted, and POSTed to `{esploraBaseUrl}/tx`, which returns the txid on success.
 
 ### User Flow
 
@@ -182,11 +182,11 @@ The send dialog has three steps:
 
 ### Additional API Endpoints
 
-| Endpoint | Purpose |
+| Endpoint (relative to `esploraBaseUrl`) | Purpose |
 |---|---|
-| `GET https://mempool.space/api/address/{address}/utxo` | Unspent transaction outputs |
-| `GET https://mempool.space/api/fee-estimates` | Recommended fee rates by block target |
-| `POST https://mempool.space/api/tx` | Broadcast signed transaction (raw hex body) |
+| `GET /address/{address}/utxo` | Unspent transaction outputs |
+| `GET /fee-estimates` | Recommended fee rates by block target |
+| `POST /tx` | Broadcast signed transaction (raw hex body) |
 
 ### Dependencies (sending-specific)
 

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "ditto",
-  "version": "2.14.3",
+  "version": "2.14.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "ditto",
-      "version": "2.14.3",
+      "version": "2.14.4",
       "dependencies": {
         "@bitcoinerlab/secp256k1": "^1.2.0",
         "@capacitor/app": "^8.0.0",

src/App.tsx

@@ -153,6 +153,7 @@ const hardcodedConfig: AppConfig = {
   imageQuality: 'compressed',
   curatorPubkey: '932614571afcbad4d17a191ee281e39eebbb41b93fac8fd87829622aeb112f4d',
   sandboxDomain: 'iframe.diy',
+  esploraBaseUrl: 'https://mempool.space/api',
   sidebarWidgets: [
     { id: 'trends' },
     { id: 'hot-posts' },

src/components/OnchainZapContent.tsx

@@ -17,6 +17,7 @@ import { useCurrentUser } from '@/hooks/useCurrentUser';
 import { useBitcoinSigner } from '@/hooks/useBitcoinSigner';
 import { useOnchainZap, type OnchainFeeSpeed } from '@/hooks/useOnchainZap';
 import { useToast } from '@/hooks/useToast';
+import { useAppContext } from '@/hooks/useAppContext';
 import { useNostrLogin } from '@nostrify/react/login';
 import {
   nostrPubkeyToBitcoinAddress,
@@ -94,6 +95,8 @@ export function OnchainZapContent({ target, onSuccess, onClose }: OnchainZapCont
   const { user } = useCurrentUser();
   const { capability } = useBitcoinSigner();
   const { logins } = useNostrLogin();
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
   const loginType = logins[0]?.type;
 
   const [usdAmount, setUsdAmount] = useState<number | string>(5);
@@ -114,21 +117,21 @@ export function OnchainZapContent({ target, onSuccess, onClose }: OnchainZapCont
     : '';
 
   const { data: btcPrice } = useQuery({
-    queryKey: ['btc-price'],
-    queryFn: fetchBtcPrice,
+    queryKey: ['btc-price', esploraBaseUrl],
+    queryFn: () => fetchBtcPrice(esploraBaseUrl),
     staleTime: 30_000,
   });
 
   const { data: utxos } = useQuery({
-    queryKey: ['bitcoin-utxos', senderAddress],
-    queryFn: () => fetchUTXOs(senderAddress),
+    queryKey: ['bitcoin-utxos', esploraBaseUrl, senderAddress],
+    queryFn: () => fetchUTXOs(senderAddress, esploraBaseUrl),
     enabled: !!senderAddress && capability !== 'unsupported',
     staleTime: 30_000,
   });
 
   const { data: feeRates } = useQuery({
-    queryKey: ['bitcoin-fee-rates'],
-    queryFn: getFeeRates,
+    queryKey: ['bitcoin-fee-rates', esploraBaseUrl],
+    queryFn: () => getFeeRates(esploraBaseUrl),
     enabled: capability !== 'unsupported',
     staleTime: 30_000,
   });

src/components/SendBitcoinDialog.tsx

@@ -33,6 +33,7 @@ import { Skeleton } from '@/components/ui/skeleton';
 import { useCurrentUser } from '@/hooks/useCurrentUser';
 import { useBitcoinSigner } from '@/hooks/useBitcoinSigner';
 import { useToast } from '@/hooks/useToast';
+import { useAppContext } from '@/hooks/useAppContext';
 import {
   nostrPubkeyToBitcoinAddress,
   npubToBitcoinAddress,
@@ -108,6 +109,8 @@ export function SendBitcoinDialog({ isOpen, onClose, btcPrice }: SendBitcoinDial
   const { user } = useCurrentUser();
   const { canSignPsbt, signPsbt } = useBitcoinSigner();
   const { toast } = useToast();
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
   const queryClient = useQueryClient();
 
   // Form state
@@ -126,15 +129,15 @@ export function SendBitcoinDialog({ isOpen, onClose, btcPrice }: SendBitcoinDial
   // ── Data fetching ──────────────────────────────────────────────
 
   const { data: utxos, isLoading: isLoadingUtxos } = useQuery({
-    queryKey: ['bitcoin-utxos', senderAddress],
-    queryFn: () => fetchUTXOs(senderAddress),
+    queryKey: ['bitcoin-utxos', esploraBaseUrl, senderAddress],
+    queryFn: () => fetchUTXOs(senderAddress, esploraBaseUrl),
     enabled: !!senderAddress && isOpen,
     staleTime: 30_000,
   });
 
   const { data: feeRates, isLoading: isLoadingFees } = useQuery({
-    queryKey: ['bitcoin-fee-rates'],
-    queryFn: getFeeRates,
+    queryKey: ['bitcoin-fee-rates', esploraBaseUrl],
+    queryFn: () => getFeeRates(esploraBaseUrl),
     enabled: isOpen,
     staleTime: 30_000,
   });
@@ -202,7 +205,7 @@ export function SendBitcoinDialog({ isOpen, onClose, btcPrice }: SendBitcoinDial
       // 3. Finalize and extract raw tx
       const txHex = finalizePsbt(signedHex);
 
-      const id = await broadcastTransaction(txHex);
+      const id = await broadcastTransaction(txHex, esploraBaseUrl);
       return { txId: id, fee };
     },
     onSuccess: ({ txId: id, fee }) => {

src/components/ZapDialog.tsx

@@ -23,6 +23,7 @@ import { useBitcoinSigner } from '@/hooks/useBitcoinSigner';
 import { useToast } from '@/hooks/useToast';
 import { useZaps } from '@/hooks/useZaps';
 import { useWallet } from '@/hooks/useWallet';
+import { useAppContext } from '@/hooks/useAppContext';
 import { canZap } from '@/lib/canZap';
 import {
   fetchBtcPrice,
@@ -287,6 +288,8 @@ export function ZapDialog({ target, children, className }: ZapDialogProps) {
   const { data: author } = useAuthor(target.pubkey);
   const { toast } = useToast();
   const { webln, activeNWC } = useWallet();
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
 
   // Success state: populated by either zap rail's onSuccess callback.
   // When set, we replace the tab UI with <ZapSuccessScreen />.
@@ -320,8 +323,8 @@ export function ZapDialog({ target, children, className }: ZapDialogProps) {
   const amountInputRef = useRef<HTMLInputElement>(null);
 
   const { data: btcPrice } = useQuery({
-    queryKey: ['btc-price'],
-    queryFn: fetchBtcPrice,
+    queryKey: ['btc-price', esploraBaseUrl],
+    queryFn: () => fetchBtcPrice(esploraBaseUrl),
     staleTime: 30_000,
   });
 

src/contexts/AppContext.ts

@@ -278,6 +278,13 @@ export interface AppConfig {
   curatorPubkey?: string;
   /** Wildcard domain used for iframe sandboxing (e.g. "iframe.diy"). Default: "iframe.diy". */
   sandboxDomain: string;
+  /**
+   * Base URL for the Esplora-compatible Bitcoin REST API. Used by the wallet,
+   * on-chain zap flows, and NIP-73 Bitcoin tx/address pages. The standard
+   * Esplora REST root (no version segment). The mempool.space `/v1/prices`
+   * extension is appended by the price call. Default: "https://mempool.space/api".
+   */
+  esploraBaseUrl: string;
   /** Ordered list of right sidebar widget configs. Each entry is a widget type ID with optional display settings. */
   sidebarWidgets: WidgetConfig[];
 }

src/hooks/useBitcoinAddress.ts

@@ -1,22 +1,27 @@
 import { useQuery } from '@tanstack/react-query';
 
 import { fetchAddressDetail, fetchBtcPrice } from '@/lib/bitcoin';
+import { useAppContext } from '@/hooks/useAppContext';
 
 /**
- * Fetch full address details (balance + recent txs) via the mempool.space API.
- * Also fetches the current BTC/USD price for display.
+ * Fetch full address details (balance + recent txs) via the configured
+ * Esplora-compatible API (default: mempool.space). Also fetches the
+ * current BTC/USD price for display.
  */
 export function useBitcoinAddress(address: string) {
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
+
   const { data: addressDetail, isLoading, error, refetch } = useQuery({
-    queryKey: ['bitcoin-address-detail', address],
-    queryFn: () => fetchAddressDetail(address),
+    queryKey: ['bitcoin-address-detail', esploraBaseUrl, address],
+    queryFn: () => fetchAddressDetail(address, esploraBaseUrl),
     enabled: !!address,
     refetchInterval: 30_000,
   });
 
   const { data: btcPrice } = useQuery({
-    queryKey: ['btc-price'],
-    queryFn: fetchBtcPrice,
+    queryKey: ['btc-price', esploraBaseUrl],
+    queryFn: () => fetchBtcPrice(esploraBaseUrl),
     refetchInterval: 60_000,
     staleTime: 30_000,
   });

src/hooks/useBitcoinTx.ts

@@ -1,22 +1,27 @@
 import { useQuery } from '@tanstack/react-query';
 
 import { fetchTxDetail, fetchBtcPrice } from '@/lib/bitcoin';
+import { useAppContext } from '@/hooks/useAppContext';
 
 /**
- * Fetch full transaction details for a Bitcoin txid via the mempool.space API.
- * Also fetches the current BTC/USD price for display.
+ * Fetch full transaction details for a Bitcoin txid via the configured
+ * Esplora-compatible API (default: mempool.space). Also fetches the
+ * current BTC/USD price for display.
  */
 export function useBitcoinTx(txid: string) {
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
+
   const { data: tx, isLoading, error } = useQuery({
-    queryKey: ['bitcoin-tx-detail', txid],
-    queryFn: () => fetchTxDetail(txid),
+    queryKey: ['bitcoin-tx-detail', esploraBaseUrl, txid],
+    queryFn: () => fetchTxDetail(txid, esploraBaseUrl),
     enabled: !!txid,
     staleTime: 60_000,
   });
 
   const { data: btcPrice } = useQuery({
-    queryKey: ['btc-price'],
-    queryFn: fetchBtcPrice,
+    queryKey: ['btc-price', esploraBaseUrl],
+    queryFn: () => fetchBtcPrice(esploraBaseUrl),
     refetchInterval: 60_000,
     staleTime: 30_000,
   });

src/hooks/useBitcoinWallet.ts

@@ -2,17 +2,21 @@ import { useMemo } from 'react';
 import { useQuery } from '@tanstack/react-query';
 
 import { useCurrentUser } from '@/hooks/useCurrentUser';
+import { useAppContext } from '@/hooks/useAppContext';
 import { nostrPubkeyToBitcoinAddress, fetchAddressData, fetchBtcPrice, fetchTransactions } from '@/lib/bitcoin';
 
 /**
  * Hook that derives a Bitcoin Taproot address from the current user's Nostr
- * pubkey and fetches the on-chain balance from the Blockstream API.
+ * pubkey and fetches the on-chain balance from the configured Esplora-compatible
+ * API (default: mempool.space).
  *
  * Balance auto-refreshes every 30 seconds while the component is mounted.
  * BTC/USD price refreshes every 60 seconds.
  */
 export function useBitcoinWallet() {
   const { user } = useCurrentUser();
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
 
   const bitcoinAddress = useMemo(() => {
     if (!user) return '';
@@ -25,15 +29,15 @@ export function useBitcoinWallet() {
     error,
     refetch,
   } = useQuery({
-    queryKey: ['bitcoin-balance', bitcoinAddress],
-    queryFn: () => fetchAddressData(bitcoinAddress),
+    queryKey: ['bitcoin-balance', esploraBaseUrl, bitcoinAddress],
+    queryFn: () => fetchAddressData(bitcoinAddress, esploraBaseUrl),
     enabled: !!bitcoinAddress,
     refetchInterval: 30_000,
   });
 
   const { data: btcPrice } = useQuery({
-    queryKey: ['btc-price'],
-    queryFn: fetchBtcPrice,
+    queryKey: ['btc-price', esploraBaseUrl],
+    queryFn: () => fetchBtcPrice(esploraBaseUrl),
     refetchInterval: 60_000,
     staleTime: 30_000,
   });
@@ -42,8 +46,8 @@ export function useBitcoinWallet() {
     data: transactions,
     isLoading: isLoadingTxs,
   } = useQuery({
-    queryKey: ['bitcoin-txs', bitcoinAddress],
-    queryFn: () => fetchTransactions(bitcoinAddress),
+    queryKey: ['bitcoin-txs', esploraBaseUrl, bitcoinAddress],
+    queryFn: () => fetchTransactions(bitcoinAddress, esploraBaseUrl),
     enabled: !!bitcoinAddress,
     refetchInterval: 30_000,
   });

src/hooks/useOnchainZap.ts

@@ -6,6 +6,7 @@ import { useCurrentUser } from '@/hooks/useCurrentUser';
 import { useBitcoinSigner, isSignerCapabilityError, reportSignerUnsupported } from '@/hooks/useBitcoinSigner';
 import { useNostrPublish } from '@/hooks/useNostrPublish';
 import { useToast } from '@/hooks/useToast';
+import { useAppContext } from '@/hooks/useAppContext';
 import { notificationSuccess } from '@/lib/haptics';
 import {
   nostrPubkeyToBitcoinAddress,
@@ -72,6 +73,8 @@ export function useOnchainZap(
   const { canSignPsbt, signPsbt } = useBitcoinSigner();
   const { mutateAsync: publishEvent } = useNostrPublish();
   const { toast } = useToast();
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
   const queryClient = useQueryClient();
 
   const [isZapping, setIsZapping] = useState(false);
@@ -101,8 +104,8 @@ export function useOnchainZap(
 
       // Fetch UTXOs and fee rates
       const [utxos, rates] = await Promise.all([
-        fetchUTXOs(senderAddress),
-        getFeeRates(),
+        fetchUTXOs(senderAddress, esploraBaseUrl),
+        getFeeRates(esploraBaseUrl),
       ]);
 
       if (utxos.length === 0) {
@@ -134,7 +137,7 @@ export function useOnchainZap(
 
       // Broadcast
       setProgress('broadcasting');
-      const txid = await broadcastTransaction(txHex);
+      const txid = await broadcastTransaction(txHex, esploraBaseUrl);
 
       // Publish kind 8333 event
       setProgress('publishing');

src/hooks/useOnchainZaps.ts

@@ -3,6 +3,7 @@ import { useNostr } from '@nostrify/react';
 import type { NostrEvent } from '@nostrify/nostrify';
 
 import { fetchTxDetail, nostrPubkeyToBitcoinAddress } from '@/lib/bitcoin';
+import { useAppContext } from '@/hooks/useAppContext';
 /** A single verified on-chain zap, with the amount that actually paid the recipient on-chain. */
 export interface OnchainZapEntry {
   /** The kind 8333 event. */
@@ -57,8 +58,14 @@ export function extractOnchainZapRecipient(event: NostrEvent): string {
  *
  * A verified amount of 0 means the transaction exists but does not pay
  * the claimed recipient — callers should discard such events.
+ *
+ * @param event       The kind 8333 event to verify.
+ * @param esploraBaseUrl  Esplora REST root used to fetch the tx detail.
  */
-export async function verifyOnchainZap(event: NostrEvent): Promise<OnchainZapEntry | null> {
+export async function verifyOnchainZap(
+  event: NostrEvent,
+  esploraBaseUrl: string,
+): Promise<OnchainZapEntry | null> {
   const txid = extractOnchainZapTxid(event);
   const recipientPubkey = extractOnchainZapRecipient(event);
   if (!txid || !recipientPubkey) return null;
@@ -73,7 +80,7 @@ export async function verifyOnchainZap(event: NostrEvent): Promise<OnchainZapEnt
 
   let detail;
   try {
-    detail = await fetchTxDetail(txid);
+    detail = await fetchTxDetail(txid, esploraBaseUrl);
   } catch {
     return null;
   }
@@ -107,6 +114,8 @@ export async function verifyOnchainZap(event: NostrEvent): Promise<OnchainZapEnt
  */
 export function useOnchainZaps(target: NostrEvent | undefined) {
   const { nostr } = useNostr();
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
   const isAddressable = target && target.kind >= 30000 && target.kind < 40000;
   const dTag = isAddressable
     ? target.tags.find(([n]) => n === 'd')?.[1] ?? ''
@@ -155,8 +164,8 @@ export function useOnchainZaps(target: NostrEvent | undefined) {
   const events = eventsQuery.data ?? [];
   const verifications = useQueries({
     queries: events.map((event) => ({
-      queryKey: ['onchain-zaps', 'verify', extractOnchainZapTxid(event), extractOnchainZapRecipient(event)],
-      queryFn: () => verifyOnchainZap(event),
+      queryKey: ['onchain-zaps', 'verify', esploraBaseUrl, extractOnchainZapTxid(event), extractOnchainZapRecipient(event)],
+      queryFn: () => verifyOnchainZap(event, esploraBaseUrl),
       staleTime: 60_000,
     })),
   });
@@ -189,12 +198,14 @@ export function useOnchainZaps(target: NostrEvent | undefined) {
  * (invalid tx, wrong recipient, self-zap, etc.), or the entry.
  */
 export function useVerifiedOnchainZap(event: NostrEvent | undefined): OnchainZapEntry | null | undefined {
+  const { config } = useAppContext();
+  const { esploraBaseUrl } = config;
   const txid = event ? extractOnchainZapTxid(event) : null;
   const recipient = event ? extractOnchainZapRecipient(event) : '';
 
   const { data } = useQuery({
-    queryKey: ['onchain-zaps', 'verify', txid, recipient],
-    queryFn: () => verifyOnchainZap(event!),
+    queryKey: ['onchain-zaps', 'verify', esploraBaseUrl, txid, recipient],
+    queryFn: () => verifyOnchainZap(event!, esploraBaseUrl),
     enabled: !!event && !!txid && !!recipient,
     staleTime: 60_000,
   });

src/lib/bitcoin.ts

@@ -8,9 +8,6 @@ import { ECPairFactory, type ECPairAPI } from 'ecpair';
 // Constants
 // ---------------------------------------------------------------------------
 
-/** Base URL for the mempool.space Esplora-compatible REST API. */
-const MEMPOOL_API = 'https://mempool.space/api';
-
 /** Standard Bitcoin dust limit in satoshis. */
 const DUST_LIMIT = 546;
 
@@ -108,11 +105,14 @@ export interface AddressData {
 }
 
 /**
- * Fetch balance and transaction stats for a Bitcoin address from the
- * mempool.space Esplora API.
+ * Fetch balance and transaction stats for a Bitcoin address from an
+ * Esplora-compatible REST API (e.g. mempool.space, Blockstream).
+ *
+ * @param address    The Bitcoin address to look up.
+ * @param baseUrl    Esplora REST root, no trailing slash (e.g. `https://mempool.space/api`).
  */
-export async function fetchAddressData(address: string): Promise<AddressData> {
-  const response = await fetch(`${MEMPOOL_API}/address/${address}`);
+export async function fetchAddressData(address: string, baseUrl: string): Promise<AddressData> {
+  const response = await fetch(`${baseUrl}/address/${address}`);
 
   if (!response.ok) {
     throw new Error('Failed to fetch balance');
@@ -156,9 +156,17 @@ export function formatSats(sats: number): string {
   return sats.toLocaleString();
 }
 
-/** Fetch the current BTC price in USD from the mempool.space API. */
-export async function fetchBtcPrice(): Promise<number> {
-  const response = await fetch(`${MEMPOOL_API}/v1/prices`);
+/**
+ * Fetch the current BTC price in USD from a mempool.space-compatible API.
+ *
+ * Note: the `/v1/prices` endpoint is a mempool.space extension to the
+ * standard Esplora REST surface. Backends like Blockstream's Esplora do
+ * not expose it.
+ *
+ * @param baseUrl    Esplora REST root, no trailing slash (e.g. `https://mempool.space/api`).
+ */
+export async function fetchBtcPrice(baseUrl: string): Promise<number> {
+  const response = await fetch(`${baseUrl}/v1/prices`);
 
   if (!response.ok) {
     throw new Error('Failed to fetch BTC price');
@@ -222,11 +230,14 @@ export interface Transaction {
 }
 
 /**
- * Fetch transactions for a Bitcoin address from the mempool.space Esplora API.
+ * Fetch transactions for a Bitcoin address from an Esplora-compatible API.
  * Returns simplified transactions with net amount relative to the address.
+ *
+ * @param address    The Bitcoin address to look up.
+ * @param baseUrl    Esplora REST root, no trailing slash.
  */
-export async function fetchTransactions(address: string): Promise<Transaction[]> {
-  const response = await fetch(`${MEMPOOL_API}/address/${address}/txs`);
+export async function fetchTransactions(address: string, baseUrl: string): Promise<Transaction[]> {
+  const response = await fetch(`${baseUrl}/address/${address}/txs`);
 
   if (!response.ok) {
     throw new Error('Failed to fetch transactions');
@@ -309,9 +320,14 @@ export interface TxDetail {
   totalOutput: number;
 }
 
-/** Fetch full transaction details from mempool.space. */
-export async function fetchTxDetail(txid: string): Promise<TxDetail> {
-  const response = await fetch(`${MEMPOOL_API}/tx/${txid}`);
+/**
+ * Fetch full transaction details from an Esplora-compatible API.
+ *
+ * @param txid       The transaction ID (hex).
+ * @param baseUrl    Esplora REST root, no trailing slash.
+ */
+export async function fetchTxDetail(txid: string, baseUrl: string): Promise<TxDetail> {
+  const response = await fetch(`${baseUrl}/tx/${txid}`);
   if (!response.ok) throw new Error('Failed to fetch transaction');
 
   const tx = await response.json();
@@ -383,11 +399,16 @@ export interface AddressDetail {
   recentTxs: Transaction[];
 }
 
-/** Fetch full address details (balance + recent txs) from mempool.space. */
-export async function fetchAddressDetail(address: string): Promise<AddressDetail> {
+/**
+ * Fetch full address details (balance + recent txs) from an Esplora-compatible API.
+ *
+ * @param address    The Bitcoin address to look up.
+ * @param baseUrl    Esplora REST root, no trailing slash.
+ */
+export async function fetchAddressDetail(address: string, baseUrl: string): Promise<AddressDetail> {
   const [addrData, txs] = await Promise.all([
-    fetchAddressData(address),
-    fetchTransactions(address),
+    fetchAddressData(address, baseUrl),
+    fetchTransactions(address, baseUrl),
   ]);
 
   return {
@@ -415,9 +436,14 @@ export interface UTXO {
   };
 }
 
-/** Fetch UTXOs for a Bitcoin address from mempool.space. */
-export async function fetchUTXOs(address: string): Promise<UTXO[]> {
-  const response = await fetch(`${MEMPOOL_API}/address/${address}/utxo`);
+/**
+ * Fetch UTXOs for a Bitcoin address from an Esplora-compatible API.
+ *
+ * @param address    The Bitcoin address to look up.
+ * @param baseUrl    Esplora REST root, no trailing slash.
+ */
+export async function fetchUTXOs(address: string, baseUrl: string): Promise<UTXO[]> {
+  const response = await fetch(`${baseUrl}/address/${address}/utxo`);
   if (!response.ok) throw new Error('Failed to fetch UTXOs');
   return response.json();
 }
@@ -436,9 +462,13 @@ export interface FeeRates {
   minimumFee: number;
 }
 
-/** Fetch recommended fee rates (sat/vB) from mempool.space. */
-export async function getFeeRates(): Promise<FeeRates> {
-  const response = await fetch(`${MEMPOOL_API}/fee-estimates`);
+/**
+ * Fetch recommended fee rates (sat/vB) from an Esplora-compatible API.
+ *
+ * @param baseUrl    Esplora REST root, no trailing slash.
+ */
+export async function getFeeRates(baseUrl: string): Promise<FeeRates> {
+  const response = await fetch(`${baseUrl}/fee-estimates`);
   if (!response.ok) throw new Error('Failed to fetch fee estimates');
 
   const data = await response.json();
@@ -477,9 +507,15 @@ export function validateBitcoinAddress(address: string): boolean {
   }
 }
 
-/** Broadcast a signed transaction hex to the Bitcoin network via mempool.space. Returns the txid. */
-export async function broadcastTransaction(txHex: string): Promise<string> {
-  const response = await fetch(`${MEMPOOL_API}/tx`, {
+/**
+ * Broadcast a signed transaction hex to the Bitcoin network via an
+ * Esplora-compatible API. Returns the txid.
+ *
+ * @param txHex      The signed transaction hex.
+ * @param baseUrl    Esplora REST root, no trailing slash.
+ */
+export async function broadcastTransaction(txHex: string, baseUrl: string): Promise<string> {
+  const response = await fetch(`${baseUrl}/tx`, {
     method: 'POST',
     body: txHex,
   });

src/lib/schemas.ts

@@ -261,6 +261,7 @@ export const AppConfigSchema = z.object({
   imageQuality: z.enum(['compressed', 'original']),
   curatorPubkey: z.string().regex(/^[0-9a-f]{64}$/i).optional(),
   sandboxDomain: z.string().optional(),
+  esploraBaseUrl: z.string().url(),
   sidebarWidgets: z.array(z.object({
     id: z.string(),
     height: z.number().optional(),

src/test/TestApp.tsx

@@ -122,6 +122,7 @@ export function TestApp({ children }: TestAppProps) {
     autoplayVideos: false,
     imageQuality: 'compressed',
     sandboxDomain: 'iframe.diy',
+    esploraBaseUrl: 'https://mempool.space/api',
     sidebarWidgets: [],
   };