Dev Highlighter

Dev Highlighter lets you turn any word or phrase into a styled, optionally-linked highlight everywhere it appears in your content — without editing a single post by hand.

Define a keyword once, choose how it should look (text colour, background colour, bold, italic, underline), optionally give it a link, and Dev Highlighter does the rest on the front end. It is built for performance: rules are compiled and cached, and content is parsed safely with DOMDocument so your markup is never mangled.

Key features

• Context-aware rules engine — one keyword can have many rules, each with its own colour, link, and target. Highlight “Mental Health” gold site-wide, green on selected pages, and blue in a category — all at once.
• Targeting — apply a rule Site-Wide, or to Selected Pages, Selected Posts, Categories, Tags, or Post Types.
• Exclusions — exclude specific posts/pages by ID, categories, or whole post types per rule.
• Priority system — when several rules match, the most specific one wins (Page › Post › Category › Tag › Post Type › Site-Wide); a per-rule priority breaks ties.
• Smart conflict detection — the admin flags keywords with multiple rules and shows which one wins.
• Future-proof architecture — a pluggable condition registry and filterable scope weights make new conditions drop-in additions.
• Unlimited keyword rules — add as many as you need.
• Styling — text colour, background colour, bold, italic, and underline per keyword.
• Auto-linking — add an optional URL to turn a keyword into a link, with optional “open in new tab” (adds rel="noopener noreferrer").
• Smart phrase protection — longer phrases always win, so “Mental Health Program” is never broken into “Mental Health” + “Program”.
• Post type control — choose exactly where processing runs: Posts, Pages, or any public custom post type.
• Safe parsing — never touches text inside script, style, textarea, pre, code, or existing links.
• Optimised CSS — identical styles are de-duplicated into shared, generated classes; no repeated inline CSS.
• Import / Export — move your rules between sites as JSON, with merge or replace.
• Performance first — compiled rules are cached in a transient and only rebuilt when a rule changes, so sites with 500+ keywords stay fast.
• Translation ready — fully internationalised with the dev-highlighter text domain.

Where processing runs

Dev Highlighter only filters the_content on the front end. It never runs in the admin area, feeds, REST requests, AJAX requests, or cron. It makes no external/third-party HTTP requests.

Extensible by design

Dev Highlighter exposes documented filters and actions (word_spotlight_condition_evaluators, word_spotlight_collect_conditions, word_spotlight_sanitize_extra_conditions, word_spotlight_rule_builder_fields, and the scope-weight filters) so optional add-ons can register new targeting conditions and rule-builder fields without modifying the core engine. An optional premium add-on, Dev Highlighter Pro, builds on these hooks; it is a separate plugin and is not required for any feature described above.