Configuration

The diff server and some diffing algorithms can be configured via environment variables. All variables are optional; defaults are noted below.

A template listing all variables is available in .env.example at the root of the repository.

Diff Settings

These variables affect the behavior of diff algorithms.

DIFFER_COLOR_INSERTION

CSS color value used to highlight insertions in html_diff_render(), links_diff(), and links_diff_html().

Default: #4dac26

DIFFER_COLOR_DELETION

CSS color value used to highlight deletions in html_diff_render(), links_diff(), and links_diff_html().

Default: #d01c8b

Server Settings

These variables affect the behavior of the diff web server.

DIFFING_SERVER_DEBUG

Set to true to enable debug mode. In debug mode, the server returns full tracebacks in error responses and automatically reloads when source files change.

Default: False

ACCESS_CONTROL_ALLOW_ORIGIN_HEADER

Value to use for the Access-Control-Allow-Origin HTTP response header, enabling CORS requests. Set to an empty string to disable the header entirely.

Default: * (allow all origins)

DIFFER_MAX_BODY_SIZE

Maximum size (in bytes) of a response body that the server will attempt to diff. Requests for content larger than this will be rejected.

Default: 10485760 (10 MB)

USE_SIMPLE_HTTP_CLIENT

Set to true to use Tornado’s built-in simple HTTP client when fetching pages to diff. By default, the server uses a cURL-based client, which is generally faster and more robust.

Default: unset (uses cURL-based client)

VALIDATE_TARGET_CERTIFICATES

Set to true to require valid SSL certificates when fetching https:// pages to diff. By default, the server does not validate SSL certificates.

Default: unset (certificates are not validated)

DIFFER_PARALLELISM

Number of diffs that can run in parallel (size of the worker process pool).

Default: unset (Tornado chooses a default based on CPU count)

MAX_DIFFS_PER_WORKER

After a worker process has completed this many diffs, it is terminated and replaced with a fresh process. This helps reclaim memory that accumulates over time. Set to 0 or leave unset to disable recycling.

Default: unset (workers run indefinitely)

RESTART_BROKEN_DIFFER

Set to true to keep accepting diff requests even if the worker process pool crashes, and attempt to restart the pool automatically. By default, a pool crash causes the server to stop accepting requests.

Default: unset (server does not restart a broken pool)