Disable Cache Before developing Drupal Theme

Step #1: Disable Aggregation

Navigate to:
Home Administration Configuration Development Performance

• Uncheck Aggregate CSS files.
• Uncheck Aggregate JavaScript files.

and save configuration. You should also clear all caches.

Step #2: Create local settings file

Copy and rename /sites/example.settings.local.php to be /sites/default/settings.local.php

Step #3: Enable local settings file

Open /sites/default/settings.php file and uncomment (remove # sign from beginning) these lines:

if (file_exists(__DIR__ . '/settings.local.php')) {
   include __DIR__ . '/settings.local.php';
 }

And add this line at the bottom. Save and close settings.php file.

$settings['cache']['bins']['page'] = 'cache.backend.null';

Step #4

Uncomment (remove # sign from the beginning) these lines in /sites/default/settings.local.php to disable the render cache and disable dynamic page cache:

$settings['cache']['bins']['render'] = 'cache.backend.null';

$settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.null';

Step #5

Find and un-comment below line in /sites/default/settings.local.php

$settings['cache']['bins']['page'] = 'cache.backend.null';

Step #6

Open /sites/development.services.yml. Delete previous codes and paste below codes.

# Local development services.
#
# To activate this feature, follow the instructions at the top of the
# 'example.settings.local.php' file, which sits next to this file.
parameters:
  http.response.debug_cacheability_headers: true
  twig.config:
    debug: true
    auto_reload: true
    cache: false
services:
  cache.backend.null:
    class: Drupal\Core\Cache\NullBackendFactory

Step #7: Rebuild

Rebuild Drupal cache by visitng following url.

example.com/core/rebuild.php

Done!!