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6.1.8 • Public • Published

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Inline and compress tags that contain the inline attribute. Supports <script>, <link>, and <img> (including *.svg sources) tags by default, and is easily extensible to handle others.

NOTE: since version 6, the API is now Promise based, and compatible with async/await, requiring a minimum Node version of 7.6

You can use inline-source-cli to run inline-source from the command line or NPM Scripts.


inlineSource(htmlpath, [options]): Promise<string>: parse htmlpath content for tags containing an inline attribute, and replace with (optionally compressed) file contents.

htmlpath can be either a filepath or a string of html content.

Available options include:

  • attribute: attribute used to parse sources (all tags will be parsed if set to false. Default 'inline')
  • compress: enable/disable compression of inlined content (default true)
  • fs: specify fs implementation (default is Node core 'fs')
  • handlers: specify custom handlers (default []) [see custom handlers]
  • ignore: disable inlining based on tag, type, and/or format (default [])
  • pretty: maintain leading whitespace when options.compress is false (default false)
  • rootpath: directory path used for resolving inlineable paths (default process.cwd())
  • saveRemote: enable/disable saving a local copy of remote sources (default true)
  • swallowErrors: enable/disable suppression of errors (default false)
  • svgAsImage: convert <img inline src="*.svg" /> to <img> and not <svg> (default false)
$ npm install inline-source
<!-- located at project/src/html/index.html -->
<!DOCTYPE html>
  <!-- inline project/www/css/inlineStyle.css as <style> -->
  <link inline href="css/inlineStyle.css">
  <!-- inline project/src/js/inlineScript.js as <script> -->
  <script inline src="../src/js/inlineScript.js"></script> 
  <!-- inline remote file as <script> -->
  <script inline src="http://js/inlineScript.js"></script> 
  <!-- inline project/www/images/inlineImage.png as base64 <img> -->
  <img inline src="images/inlineImage.png" />
  <!-- inline project/www/images/inlineImage.svg as <svg> -->
  <img inline src="images/inlineImage.svg" />
const { inlineSource } = require('inline-source');
const fs = require('fs');
const path = require('path');
const htmlpath = path.resolve('project/src/html/index.html');
inlineSource(htmlpath, {
  compress: true,
  rootpath: path.resolve('www'),
  // Skip all css types and png formats
  ignore: ['css', 'png']
}).then(html => {
  // Do something with html
}).catch(err => {
  // Handle error

...or preferably using async/await:

const { inlineSource } = require('inline-source');
const fs = require('fs');
const path = require('path');
const htmlpath = path.resolve('project/src/html/index.html');
let html;
try {
  html = await inlineSource(htmlpath, {
    compress: true,
    rootpath: path.resolve('www'),
    // Skip all css types and png formats
    ignore: ['css', 'png']
  // Do something with html
} catch(err) {
  // Handle error

Custom Handlers

Custom handlers are simple middleware-type functions that enable you to provide new, or override existing, inlining behaviour. All handlers have the following signature: (source, context) => Promise

  • source: the current source object to act upon

    • attributes: the parsed tag attributes object
    • compress: the compress flag (may be overriden at the tag level via props)
    • content: the processed fileContent string
    • extension: the file extension
    • fileContent: the loaded file content string
    • filepath: the fully qualified path string
    • format: the format string (jpg, gif, svg+xml, etc)
    • match: the matched html tag string, including closing tag if appropriate
    • props: the parsed namespaced attributes object (see props)
    • replace: the tag wrapped content string to replace match
    • tag: the tag string (script, link, etc)
    • type: the content type based on type mime-type attribute, or tag (js for application/javascript, css for text/css, etc)
  • context: the global context object storing all configuration options (attribute, compress, ignore, pretty, rootpath, swallowErrors, svgAsImage), in addtion to:

    • html: the html file's content string
    • htmlpath: the html file's path string
    • sources: the array of source objects

Custom handlers are inserted before the defaults, enabling overriding of default behaviour:

module.exports = function customjs(source, context) {
  if (source.fileContent && !source.content && source.type == 'js') {
    source.content = "Hey! I'm overriding the file's content!";
  return Promise.resolve();

In general, default file content processing will be skipped if source.content is already set, and default wrapping of processed content will be skipped if source.replace is already set.


Source props are a subset of attributes that are namespaced with the current global attribute ('inline' by default), and allow declaratively passing data or settings to handlers:

<script inline inline-foo="foo" inline-compress="false" src="../src/js/inlineScript.js"></script>
module.exports = function customjs(source, context) {
  if (source.fileContent && !source.content && source.type == 'js') {
    // The `inline-compress` attribute automatically overrides the global flag
    if (!source.compress) {
      // do something
    if (source.props.foo == 'foo') {
      // foo content
  return Promise.resolve();


npm i inline-source

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