Sanctum

Block distracting websites and add a deliberate pause before opening them.

Sanctum – Block Distractions, Build Focus, Stay in Control Sanctum is a free, privacy-first website blocker and focus timer for Chrome. It helps you stop compulsive browsing, block distracting or harmful sites, and replace the habit of mindless scrolling with intentional, structured focus sessions — all without sending a single byte of your data to any server. **Who Is Sanctum For?** Sanctum is built for anyone who has ever opened a browser tab with one intention and found themselves somewhere completely different twenty minutes later — someone who struggles with adult content, gambling sites, social media rabbit holes, short video feeds, or any other corner of the internet that pulls attention away from work, study, or recovery. It is for the student who keeps drifting to video sites instead of finishing an assignment. It is for the professional who loses hours every week to social feeds during work hours. It is for anyone trying to break a habit around adult content or gambling who needs more friction than willpower alone can provide. It is for anyone who has tried other blockers, found them too expensive, and wanted a fully functional free alternative built with genuine care. **Core Problem: Willpower Alone Is Not Enough** Modern websites are engineered to capture and hold attention. Every scroll, notification, and recommendation is designed to override the user's original intention. Blocking them with willpower is a daily losing battle. Sanctum changes the equation: instead of fighting the pull, it inserts structured friction — a block page, a password prompt, a cooldown — that gives the user's rational mind just enough time to regain control. **What Sanctum Does** **1. Website Blocking — Domain and URL Rules** Users can add any domain or URL pattern to a personal block list. When a blocked site is visited, Chrome redirects to Sanctum's block page instead of loading the site. Rules are applied using Chrome's declarativeNetRequest API, which means blocking happens at the network request level — fast, efficient, and without reading page content. Rules can be: - Domain-level (e.g., example.com blocks all pages on that domain) - Subdomain-aware (a rule for example.com also catches www.example.com) - URL-keyword-based (block any URL that contains a specific string) A quick-block button in the popup lets users block the currently open tab's domain with a single click, so adding a site takes under three seconds. **2. Category Blocking — Five Preset Categories** For users who do not want to manually maintain a block list, Sanctum ships with five pre-built categories, each containing dozens of well-known domains and URL patterns: - **Adult Content** — Covers major adult video sites, live cam platforms, and related domains, including both international and region-specific sites commonly accessed across Asia, North America, and Europe. - **Gambling** — Covers online casinos, sports betting platforms, poker sites, lottery portals, and bookmakers from multiple regions. - **Social Media** — Covers major global social networks, messaging apps, and community platforms, including both Western and Asian services across desktop and mobile web. - **Short Video** — Covers major short-form video platforms and feed-style video apps popular across Western and Asian markets, including vertical video feeds and auto-play recommendation surfaces. - **Gaming** — Covers major game stores, gaming news sites, live-streaming and esports platforms, and game-related communities. Users enable or disable each category in one click. Categories are cumulative with the manual block list, so users can combine both approaches. **3. Custom Keywords — Extend Any Category** Beyond the preset domain lists, users can add their own keywords to any category. If a URL path, query string, or hostname contains the keyword, the request is blocked. This lets users catch niche sites not covered by the built-in lists without needing to manage full domain rules. **4. Allowlist — Exceptions That Always Pass** Users can add any domain to a permanent allowlist. Allowed domains bypass all blocking rules regardless of category settings. This lets users whitelist a work-related social media account, an employer's gaming platform, or any other legitimate exception, without disabling the broader category block. **5. Focus Timer — Pomodoro-Style Structured Work Sessions** Sanctum includes a built-in focus timer with three intensity modes and flexible session lengths. Session lengths: 25 minutes, 45 minutes, 60 minutes, or a custom duration from 1 to 480 minutes. Focus modes: - **Light Focus** — Only the user's custom block list is enforced during the session. Suitable for users who only need to block a specific set of sites while still being able to browse general content. - **Deep Focus** — Enforces the custom block list and additionally blocks all Social Media, Short Video, and Gaming categories automatically during the session, regardless of whether those categories are toggled on in the blocklist tab. Designed for deep work that requires isolation from entertainment and social distractions. - **Extreme Focus** — Whitelist mode. Only domains the user has explicitly added to the allowlist are accessible during the session. All other URLs are blocked. The most restrictive mode, suitable for study sprints or writing sessions where the user wants zero access to anything except a few approved resources. During a session, the popup shows a live countdown ring, the current elapsed time, and a real-time count of how many block attempts were intercepted during that session ("X distractions blocked this round"). Sessions can be paused and resumed. Ending a session early requires a confirmation step to prevent accidental dismissal. After a session ends, Sanctum transitions to a 5-minute rest timer with optional early exit. **6. Password Protection — Real Friction Against Impulse** Users can set a protection password stored as a salted PBKDF2 hash (150,000 iterations) — never as plaintext. Once enabled, modifying block rules, disabling categories, or turning off protection requires entering the correct password. Authentication sessions expire after 2 minutes of inactivity, so a user cannot bypass protection by leaving the popup open. This is the single most important anti-circumvention feature. When a user feels the impulse to remove a block, the password prompt adds a moment of deliberate friction — enough time for the rational decision to override the impulsive one. **7. Temporary Access Windows** If a user has a legitimate reason to visit a blocked site (for example, a work task that requires checking a social media profile), they can request a 5-minute temporary access window from the block page. The window is created as a Chrome session rule that expires automatically. When it expires, the block resumes without any action required from the user. **8. Block Page with Motivational Context** When a user hits a blocked site, Sanctum redirects to a custom block page. The page shows the blocked domain, which rule triggered the block, and a motivational message. The block page is designed to be visually distinct from the normal browser — calm, focused, with no dark-pattern elements that encourage the user to find a workaround. Options on the page are: go back, request temporary access (if not password-protected), or enter the password. **9. Statistics and Progress Tracking** The Stats tab provides a comprehensive view of the user's focus and blocking history: - **Today at a glance:** Today's total focus time, total block attempts, and longest single focus session. - **Daily focus goal:** Users set a daily focus target (default 240 minutes). The header always shows progress toward today's goal. - **Weekly focus chart:** A bar chart showing daily focus minutes across the past 7 days, with comparison to the prior week. - **Weekly block trend:** A line chart showing daily block attempts across the past 7 days. - **Energy heatmap:** A 7-day grid showing focus intensity per day, similar to a GitHub contribution graph. - **Top blocked sites:** A ranked list of the domains that triggered the most block attempts, showing which sites were hardest to resist. - **Streak tracking:** Consecutive days of meeting the daily focus goal, with current and longest streak shown. - **Focus profile:** Behavioral patterns based on session history (time of day, session length distribution, etc.). - **Achievements:** A gamified progress system with seven milestone badges — First Focus, 7-Day Streak, 100 Blocks Resisted, 10 Hours Focused, 30-Day Streak, 100 Hours Focused, and Night Owl (10 late-night sessions). Achievements are calculated locally and shown in the Stats tab. - **Monthly report:** A one-click generated monthly summary exportable as a text report. **10. Accountability Partner Mode** Users can enter a partner's name and email address in the HQ settings panel. When enabled, Sanctum can open a pre-composed email draft addressed to the partner — for example, when the user wants to share a weekly progress summary or acknowledge a difficult day. The draft is opened in the user's default mail client; Sanctum does not send email automatically or access the user's email account. **11. Optional Enhanced Page Scan (Off by Default)** Sanctum includes an optional local page scanner that is disabled by default. When the user explicitly enables it, Sanctum registers a content script that checks the page URL, page title, meta description, meta keywords, Open Graph fields, headings, and a limited amount of visible body text on the device. This scan is used to detect adult-content pages that were not already matched by domain rules — for example, a site that hosts mixed content and only some pages are problematic. When the scanner identifies a page as likely adult content with high confidence, it stores only the hostname, category, timestamp, and confidence score locally so future visits to that hostname can be intercepted at the network level. No page text is uploaded or stored. The scanner explicitly skips form fields, inputs, textareas, password fields, iframes, and payment sections. The enhanced scan can be turned off at any time from the settings panel. **12. Data Management — Export, Clear, and Reset** Users can export all local data (block rules, category settings, custom keywords, allowlist, focus statistics) as a JSON file from the HQ settings panel. Password hashes and any authentication tokens are redacted from exports. Users can also clear all local data from the same panel, or remove the extension entirely from Chrome to delete all extension storage. **13. Onboarding and First-Run Experience** On first install, Sanctum opens an onboarding page that walks the user through: what the extension does, what each permission is used for, how the privacy model works, and how to set an initial protection password and starter blocking category. The onboarding page is skippable and can be accessed again from the settings panel. Language (English or Chinese) can be selected during onboarding. Privacy — No Data Leaves Your Device All blocking rules, category settings, custom keywords, focus session history, statistics, password hashes, and allowlists are stored exclusively in Chrome's local storage on the user's device. Sanctum does not have a backend server. Sanctum does not collect, transmit, or sell any user data. There is no account system in the current version. There is no analytics or telemetry. The extension does not read or upload page content for core blocking. The optional enhanced page scanner processes content locally and stores only a hostname and metadata — never full page text. Permissions and Why Each Is Required - **storage** — Saves block rules, category toggles, custom keywords, focus session data, statistics, settings, and the password hash on the device. - **activeTab** — Reads the hostname of the currently open tab so the popup can show whether that site is blocked and offer a quick-block button. - **declarativeNetRequest** — Applies blocking rules at the network request level. This is the standard Manifest V3 API for URL blocking; it does not give the extension access to page content or request bodies. - **alarms** — Manages timers for focus session expiry, rest period end, and temporary access window expiry. Chrome's Alarm API is used because service workers do not maintain persistent timers across browser restarts. - **notifications** — Sends an optional desktop notification when a focus session ends or a rest period completes. This permission is used only for these two events and only if the user has not disabled notifications in settings. - **scripting** — Required to dynamically register the optional enhanced page scanner content script when the user enables it. The content script is not injected by default and only activates after the user explicitly turns on the enhanced scan in settings. - **host_permissions: \<all_urls\>** — Required because user-configured block rules can apply to any domain. If this permission covered only a fixed list of domains, users could not block sites of their own choosing. This permission does not allow the extension to read page content; it enables declarativeNetRequest rules to match requests across all URLs the user has configured. Comparison With Existing Solutions Most well-known website blockers (Freedom, Cold Turkey, StayFocusd, BlockSite) charge monthly or annual subscription fees ranging from $3 to $10 per month. Sanctum provides comparable or superior core functionality — domain blocking, category blocking, password protection, focus timer with multiple modes, and usage statistics — entirely free, with a stronger local-first privacy model and no account requirement. Summary Install Sanctum if you want to: - Block specific websites, adult content, gambling sites, or social media with one click - Add real friction (password protection) so impulsive access is harder to execute - Run structured focus sessions that automatically enforce stricter blocking during work time - Track how many distractions you resisted and how much focused time you actually accumulated - Keep all of your data on your own device with no server, no account, and no subscription Sanctum is a single-purpose extension: it helps users configure, apply, and maintain intentional access rules for their own browser, with the goal of reducing compulsive and distracting browsing behavior.