diff --git a/backend/src/api/common.ts b/backend/src/api/common.ts
index ca6e2c1cc..c3e0f1a42 100644
--- a/backend/src/api/common.ts
+++ b/backend/src/api/common.ts
@@ -25,4 +25,26 @@ export class Common {
     arr.push(transactions[lastindex].feePerVsize);
     return arr;
   }
+
+  static findRbfTransactions(added: TransactionExtended[], deleted: TransactionExtended[]): { [txid: string]: TransactionExtended } {
+    const matches: { [txid: string]: TransactionExtended } = {};
+    deleted
+      // The replaced tx must have at least one input with nSequence < maxint-1 (That’s the opt-in)
+      .filter((tx) => tx.vin.some((vin) => vin.sequence < 0xfffffffe))
+      .forEach((deletedTx) => {
+        const foundMatches = added.find((addedTx) => {
+          // The new tx must, absolutely speaking, pay at least as much fee as the replaced tx.
+          return addedTx.fee > deletedTx.fee
+            // The new transaction must pay more fee per kB than the replaced tx.
+            && addedTx.feePerVsize > deletedTx.feePerVsize
+            // Spends one or more of the same inputs
+            && deletedTx.vin.some((deletedVin) =>
+              addedTx.vin.some((vin) => vin.txid === deletedVin.txid));
+            });
+        if (foundMatches) {
+          matches[deletedTx.txid] = foundMatches;
+        }
+      });
+    return matches;
+  }
 }
diff --git a/backend/src/api/mempool-blocks.ts b/backend/src/api/mempool-blocks.ts
index 3381bf237..353c11b1d 100644
--- a/backend/src/api/mempool-blocks.ts
+++ b/backend/src/api/mempool-blocks.ts
@@ -49,9 +49,9 @@ class MempoolBlocks {
         transactions.push(tx);
       } else {
         mempoolBlocks.push(this.dataToMempoolBlocks(transactions, blockSize, blockVSize, mempoolBlocks.length));
-        blockVSize = 0;
-        blockSize = 0;
-        transactions = [];
+        blockVSize = tx.vsize;
+        blockSize = tx.size;
+        transactions = [tx];
       }
     });
     if (transactions.length) {
diff --git a/backend/src/api/mempool.ts b/backend/src/api/mempool.ts
index abc6a5c46..7e083e56c 100644
--- a/backend/src/api/mempool.ts
+++ b/backend/src/api/mempool.ts
@@ -123,31 +123,30 @@ class Mempool {
         }
       }
 
-      // Replace mempool to clear already confirmed transactions
+      // Replace mempool to clear deleted transactions
       const newMempool = {};
-      transactions.forEach((tx) => {
-        if (this.mempoolCache[tx]) {
+      const deletedTransactions: Transaction[] = [];
+      for (const tx in this.mempoolCache) {
+        if (transactions.indexOf(tx) > -1) {
           newMempool[tx] = this.mempoolCache[tx];
         } else {
-          hasChange = true;
+          deletedTransactions.push(this.mempoolCache[tx]);
         }
-      });
+      }
 
       if (!this.inSync && transactions.length === Object.keys(newMempool).length) {
         this.inSync = true;
         console.log('The mempool is now in sync!');
       }
 
-      console.log(`New mempool size: ${Object.keys(newMempool).length} Change: ${diff}`);
-
-      this.mempoolCache = newMempool;
-
-      if (hasChange && this.mempoolChangedCallback) {
-        this.mempoolChangedCallback(this.mempoolCache, newTransactions);
+      if (this.mempoolChangedCallback && (hasChange || deletedTransactions.length)) {
+        this.mempoolCache = newMempool;
+        this.mempoolChangedCallback(this.mempoolCache, newTransactions, deletedTransactions);
       }
 
       const end = new Date().getTime();
       const time = end - start;
+      console.log(`New mempool size: ${Object.keys(newMempool).length} Change: ${diff}`);
       console.log('Mempool updated in ' + time / 1000 + ' seconds');
     } catch (err) {
       console.log('getRawMempool error.', err);
diff --git a/backend/src/api/websocket-handler.ts b/backend/src/api/websocket-handler.ts
index f29d7a8bb..87e187c9f 100644
--- a/backend/src/api/websocket-handler.ts
+++ b/backend/src/api/websocket-handler.ts
@@ -8,6 +8,7 @@ import backendInfo from './backend-info';
 import mempoolBlocks from './mempool-blocks';
 import fiatConversion from './fiat-conversion';
 import * as os from 'os';
+import { Common } from './common';
 
 class WebsocketHandler {
   private wss: WebSocket.Server | undefined;
@@ -121,7 +122,8 @@ class WebsocketHandler {
     });
   }
 
-  handleMempoolChange(newMempool: { [txid: string]: TransactionExtended }, newTransactions: TransactionExtended[]) {
+  handleMempoolChange(newMempool: { [txid: string]: TransactionExtended },
+    newTransactions: TransactionExtended[], deletedTransactions: TransactionExtended[]) {
     if (!this.wss) {
       throw new Error('WebSocket.Server is not set');
     }
@@ -130,6 +132,7 @@ class WebsocketHandler {
     const mBlocks = mempoolBlocks.getMempoolBlocks();
     const mempoolInfo = memPool.getMempoolInfo();
     const vBytesPerSecond = memPool.getVBytesPerSecond();
+    const rbfTransactions = Common.findRbfTransactions(newTransactions, deletedTransactions);
 
     this.wss.clients.forEach((client: WebSocket) => {
       if (client.readyState !== WebSocket.OPEN) {
@@ -204,6 +207,15 @@ class WebsocketHandler {
         }
       }
 
+      if (client['track-tx'] && rbfTransactions[client['track-tx']]) {
+        for (const rbfTransaction in rbfTransactions) {
+          if (client['track-tx'] === rbfTransaction) {
+            response['rbfTransaction'] = rbfTransactions[rbfTransaction];
+            break;
+          }
+        }
+      }
+
       if (Object.keys(response).length) {
         client.send(JSON.stringify(response));
       }
@@ -228,7 +240,7 @@ class WebsocketHandler {
         }
       }
 
-      matchRate = Math.ceil((matches.length / txIds.length) * 100);
+      matchRate = Math.round((matches.length / (txIds.length - 1)) * 100);
       if (matchRate > 0) {
         const currentMemPool = memPool.getMempool();
         for (const txId of matches) {
diff --git a/backend/src/interfaces.ts b/backend/src/interfaces.ts
index 341cee0de..f14561847 100644
--- a/backend/src/interfaces.ts
+++ b/backend/src/interfaces.ts
@@ -35,9 +35,6 @@ export interface Transaction {
 }
 
 export interface TransactionExtended extends Transaction {
-  txid: string;
-  fee: number;
-  size: number;
   vsize: number;
   feePerVsize: number;
   firstSeen: number;
diff --git a/frontend/src/app/components/transaction/transaction.component.html b/frontend/src/app/components/transaction/transaction.component.html
index 17846964d..397971e93 100644
--- a/frontend/src/app/components/transaction/transaction.component.html
+++ b/frontend/src/app/components/transaction/transaction.component.html
@@ -1,6 +1,14 @@
 <div class="container-xl">
 
   <div class="title-block">
+    <div *ngIf="rbfTransaction" class="alert alert-mempool" role="alert">
+      This transaction has been replaced by:
+      <a class="alert-link" [routerLink]="['/tx/' | relativeUrl, rbfTransaction.txid]" [state]="{ data: rbfTransaction }">
+        <span class="d-inline d-lg-none">{{ rbfTransaction.txid | shortenString : 24 }}</span>
+        <span class="d-none d-lg-inline">{{ rbfTransaction.txid }}</span>
+      </a>
+    </div>
+  
     <h1 class="float-left mr-3 mb-md-3">Transaction</h1>
 
     <ng-template [ngIf]="tx?.status?.confirmed">
diff --git a/frontend/src/app/components/transaction/transaction.component.ts b/frontend/src/app/components/transaction/transaction.component.ts
index 7b0bfd2b6..4568e4cee 100644
--- a/frontend/src/app/components/transaction/transaction.component.ts
+++ b/frontend/src/app/components/transaction/transaction.component.ts
@@ -36,6 +36,7 @@ export class TransactionComponent implements OnInit, OnDestroy {
     potentialP2shGains: 0,
   };
   isRbfTransaction: boolean;
+  rbfTransaction: undefined | Transaction;
 
   constructor(
     private route: ActivatedRoute,
@@ -126,6 +127,9 @@ export class TransactionComponent implements OnInit, OnDestroy {
         this.audioService.playSound('magic');
         this.findBlockAndSetFeeRating();
       });
+
+    this.stateService.txReplaced$
+      .subscribe((rbfTransaction) => this.rbfTransaction = rbfTransaction);
   }
 
   handleLoadElectrsTransactionError(error: any): Observable<any> {
@@ -198,6 +202,7 @@ export class TransactionComponent implements OnInit, OnDestroy {
     this.feeRating = undefined;
     this.waitingForTransaction = false;
     this.isLoadingTx = true;
+    this.rbfTransaction = undefined;
     this.transactionTime = -1;
     document.body.scrollTo(0, 0);
     this.leaveTransaction();
diff --git a/frontend/src/app/interfaces/websocket.interface.ts b/frontend/src/app/interfaces/websocket.interface.ts
index eabff1583..6c59a4b6b 100644
--- a/frontend/src/app/interfaces/websocket.interface.ts
+++ b/frontend/src/app/interfaces/websocket.interface.ts
@@ -11,6 +11,7 @@ export interface WebsocketResponse {
   action?: string;
   data?: string[];
   tx?: Transaction;
+  rbfTransaction?: Transaction;
   'track-tx'?: string;
   'track-address'?: string;
   'track-asset'?: string;
diff --git a/frontend/src/app/services/state.service.ts b/frontend/src/app/services/state.service.ts
index f0c32ee98..4cd6a72ea 100644
--- a/frontend/src/app/services/state.service.ts
+++ b/frontend/src/app/services/state.service.ts
@@ -24,6 +24,7 @@ export class StateService {
   mempoolStats$ = new ReplaySubject<MemPoolState>(1);
   mempoolBlocks$ = new ReplaySubject<MempoolBlock[]>(1);
   txConfirmed$ = new Subject<Block>();
+  txReplaced$ = new Subject<Transaction>();
   mempoolTransactions$ = new Subject<Transaction>();
   blockTransactions$ = new Subject<Transaction>();
 
diff --git a/frontend/src/app/services/websocket.service.ts b/frontend/src/app/services/websocket.service.ts
index 9be503356..65846df7f 100644
--- a/frontend/src/app/services/websocket.service.ts
+++ b/frontend/src/app/services/websocket.service.ts
@@ -89,6 +89,10 @@ export class WebsocketService {
           this.stateService.conversions$.next(response.conversions);
         }
 
+        if (response.rbfTransaction) {
+          this.stateService.txReplaced$.next(response.rbfTransaction);
+        }
+
         if (response['mempool-blocks']) {
           this.stateService.mempoolBlocks$.next(response['mempool-blocks']);
         }
diff --git a/frontend/src/styles.scss b/frontend/src/styles.scss
index b53685633..268ce2238 100644
--- a/frontend/src/styles.scss
+++ b/frontend/src/styles.scss
@@ -410,3 +410,9 @@ h1, h2, h3 {
 .tooltip-inner {
   max-width: inherit;
 }
+
+.alert-mempool {
+  color: #ffffff;
+  background-color: #653b9c;
+  border-color: #3a1c61;
+}