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---
lang: en
title: 'API docs: rest.restapplication.expressmiddleware'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/rest
permalink: /doc/en/lb4/apidocs.rest.restapplication.expressmiddleware.html
---
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[Home](./index.md) > [@loopback/rest](./rest.md) > [RestApplication](./rest.restapplication.md) > [expressMiddleware](./rest.restapplication.expressmiddleware.md)
## RestApplication.expressMiddleware() method
Bind an Express middleware to this server context
**Signature:**
```typescript
expressMiddleware(key: BindingAddress, middleware: ExpressRequestHandler | ExpressRequestHandler[], options?: MiddlewareBindingOptions): Binding<Middleware>;
```
## Parameters
<table><thead><tr><th>
Parameter
</th><th>
Type
</th><th>
Description
</th></tr></thead>
<tbody><tr><td markdown="1">
key
</td><td markdown="1">
[BindingAddress](./context.bindingaddress.md)
</td><td markdown="1">
Middleware binding key
</td></tr>
<tr><td markdown="1">
middleware
</td><td markdown="1">
ExpressRequestHandler \| ExpressRequestHandler\[\]
</td><td markdown="1">
Express middleware handler function(s)
</td></tr>
<tr><td markdown="1">
options
</td><td markdown="1">
MiddlewareBindingOptions
</td><td markdown="1">
_(Optional)_
</td></tr>
</tbody></table>
**Returns:**
[Binding](./context.binding.md)<!-- --><Middleware>
## Example
```ts
import myExpressMiddlewareFactory from 'my-express-middleware';
const myExpressMiddlewareConfig= {};
const myExpressMiddleware = myExpressMiddlewareFactory(myExpressMiddlewareConfig);
server.expressMiddleware('middleware.express.my', myExpressMiddleware);
```