Email Reply Parser

Email Reply Parser is a node library to parse plain-text email replies and extract content

This library supports most email replies, signatures and locales.

😘 Maintainer: @baptistejamin

Who uses it?

Crisp

👋 You use this library and you want to be listed there? Contact us.

Installation

Install the project using NPM:

npm install --save @clearfeed-ai/email-reply-parser

RE2 Support

By default, the library relies on the RE2 regex engine, which provides better performance and avoids issues like ReDOS. By default, RE2 will be installed as a peer dependency.

If you want to explicitly exclude RE2, then npm uninstall re2.

Features

This library is used at Crisp everyday with around 1 million inbound emails. Over the years, we improved this library so it can work with most emails.

• Strip email replies like On DATE, NAME <EMAIL> wrote:
• Supports around 10 locales, including English, French, Spanish, Portuguese, Italian, Japanese, Chinese.
• Removes signatures like Sent from my iPhone
• Removes signatures like Best wishes

Usage

var EmailReplyParser = require("@clearfeed-ai/email-reply-parser");

var email =  new EmailReplyParser().read(MY_EMAIL_STRING);

console.log(email.getVisibleText());

Basic Example

var EmailReplyParser = require("@clearfeed-ai/email-reply-parser");

var emailContent = `Hi there,

I appreciate your help with this issue.

Thanks!

On Jan 28, 2026, at 10:00 AM, Support <support@example.com> wrote:

> How can I help you?
> 
> Best regards,
> Support Team`;

var parser = new EmailReplyParser();
var reply = parser.parseReply(emailContent);

console.log(reply);
// Output: "Hi there,\n\nI appreciate your help with this issue."

Custom Regex Patterns

You can add custom header and signature regex patterns at runtime to handle specific email formats that aren't covered by the default patterns.

Adding Custom Quote Header Patterns

Quote headers are patterns that indicate quoted or forwarded content (e.g., "On DATE, NAME wrote:").

var EmailReplyParser = require("@clearfeed-ai/email-reply-parser");

var parser = new EmailReplyParser();

// Add one or more custom quote header regexes
parser.addQuoteHeaderRegexes([
  /^Forwarded by .+ on .+$/m,
  /^Original message from .+$/m,
  /^----- Reply from .+ -----$/m
]);

// Now parse emails with these custom patterns
var email = parser.read(emailContent);

Adding Custom Signature Patterns

Signature patterns identify signature lines that should be removed (e.g., "Sent from my iPhone", "Best regards").

var EmailReplyParser = require("@clearfeed-ai/email-reply-parser");

var parser = new EmailReplyParser();

// Add one or more custom signature regexes
parser.addSignatureRegexes([
  /^Sent via CompanyName Mobile$/,
  /^Thanks,?$/mi,
  /^Have a great day!?$/mi,
  /^Posted using MyApp$/
]);

// Now parse emails with these custom patterns
var email = parser.read(emailContent);

Resetting to Default Patterns

If you need to reset the patterns back to the defaults:

var EmailReplyParser = require("@clearfeed-ai/email-reply-parser");

var parser = new EmailReplyParser();

// Add custom patterns
parser.addQuoteHeaderRegexes([/^Custom pattern$/m]);

// Reset to default quote header patterns
parser.resetQuoteHeaderRegexes();

// Reset to default signature patterns
parser.resetSignatureRegexes();

Method Chaining

All custom regex methods support method chaining for convenience:

var EmailReplyParser = require("@clearfeed-ai/email-reply-parser");

var email = new EmailReplyParser()
  .addQuoteHeaderRegexes([/^Forwarded by .+$/m])
  .addSignatureRegexes([/^Sent via MyApp$/])
  .read(emailContent);

Note: Custom patterns are added globally and will affect all subsequent parsing operations. In multi-tenant environments, reset the patterns between tenants or avoid registering tenant-specific patterns globally.

Contributing

Feel free to fork this project and submit fixes. We may adapt your code to fit the codebase.

You can run unit tests using:

npm test

Credits

• GitHub
• William Durand william.durand1@gmail.com
• Crisp IM

License

email-reply-parser is released under the MIT License. See the bundled LICENSE file for details.