CORS Policy Configuration for 1C-Bitrix API

We often encounter a situation where a frontend application at app.example.com makes requests to an API at api.example.com (or to Bitrix24 REST methods), and the browser blocks the request due to CORS. Classic pain: a developer spends hours searching for the error, even though the problem is solved by adding three headers. CORS configuration is not about protecting the server (server-side requests are unaffected by CORS), but about allowing your JavaScript to work with cross-origin requests. Over 10 years of working with Bitrix, we have solved CORS problems for 200+ projects, saving clients an average of 20–40 thousand rubles on debugging.

How CORS Requests Work

CORS (Cross-Origin Resource Sharing) is a browser security mechanism that blocks requests to a domain different from the page domain. Simple requests (GET, POST with Content-Type: application/x-www-form-urlencoded) are sent directly by the browser, but it checks the response: if there is no Access-Control-Allow-Origin header with the correct value, JavaScript does not receive the response (the request was sent, the server responded, but the browser hid it from JS). Preflight requests are for non-standard methods (PUT, DELETE, PATCH) and headers (Authorization, Content-Type: application/json). The browser first sends an OPTIONS request (“Can I do this?”), the server responds—and only then the browser sends the actual request.

When Is a Preflight Request Needed?

Any request with a Content-Type other than application/x-www-form-urlencoded, such as application/json, or with a custom header (e.g., X-API-Key) triggers a preflight. Preflight also occurs when using methods other than GET/POST. This feature is important to consider when designing a REST API—if your client sends JSON, be ready to handle OPTIONS.

How to Configure CORS on Nginx

For an on-premise Bitrix API, CORS is best configured in Nginx, not PHP. Nginx handles OPTIONS preflight without starting PHP, giving a performance gain of up to 15 ms per request.

location /api/ {
    # List of allowed origins
    set $cors_origin "";
    if ($http_origin ~* "^https://(app\.example\.com|admin\.example\.com)$") {
        set $cors_origin $http_origin;
    }

    # Preflight OPTIONS
    if ($request_method = OPTIONS) {
        add_header Access-Control-Allow-Origin $cors_origin always;
        add_header Access-Control-Allow-Methods "GET, POST, PUT, DELETE, PATCH, OPTIONS" always;
        add_header Access-Control-Allow-Headers "Authorization, Content-Type, X-API-Key" always;
        add_header Access-Control-Max-Age 3600 always;
        add_header Content-Length 0;
        return 204;
    }

    add_header Access-Control-Allow-Origin $cors_origin always;
    add_header Access-Control-Allow-Credentials true always;

    proxy_pass http://php_backend;
}

Access-Control-Allow-Credentials: true is needed if requests carry cookies (Bitrix sessions). In this case, Access-Control-Allow-Origin cannot be *—only a specific domain.

Configuration via PHP (init.php or middleware)

If CORS needs to be configured dynamically (different rules for different endpoints, origin list from DB):

// /local/php_interface/init.php or API middleware
$allowedOrigins = ['https://app.example.com', 'https://admin.example.com'];
$origin = $_SERVER['HTTP_ORIGIN'] ?? '';

if (in_array($origin, $allowedOrigins)) {
    header('Access-Control-Allow-Origin: ' . $origin);
    header('Access-Control-Allow-Credentials: true');
    header('Vary: Origin'); // Important for proper CDN caching
}

if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    header('Access-Control-Allow-Methods: GET, POST, PUT, DELETE, PATCH, OPTIONS');
    header('Access-Control-Allow-Headers: Authorization, Content-Type, X-API-Key');
    header('Access-Control-Max-Age: 3600');
    http_response_code(204);
    exit;
}

The Vary: Origin header is mandatory with dynamic CORS—MDN Web Docs recommend it for proper CDN caching.

CORS for Bitrix24 REST API

Cloud Bitrix24 cannot be configured—CORS headers are managed on the Bitrix side. For browser requests to portal.bitrix24.ru/rest/, use the built-in JS-SDK (BX24.callMethod), which works inside an iframe application and is not subject to CORS restrictions. Direct REST requests from the browser to a different Bitrix24 domain require proxying through your server. More details in the official documentation.

Why Can't You Use * with Credentials?

Access-Control-Allow-Origin: * allows everyone. But with Access-Control-Allow-Credentials: true, this is not allowed—the browser will block such a response. Only specific domains are permitted.

Validate the origin list. A check like if ($origin === 'https://app.example.com') is not bypassed by an attacker with header Origin: https://app.example.com. No—this is not a bypass: CORS protects against browser attacks, not against curl. Server-side requests ignore CORS.

Preflight cache (Max-Age). A value of 3600 means the browser does not send a repeated OPTIONS request for one hour. A too large value slows down detection of CORS policy changes.

Typical Scenarios Requiring CORS Configuration

How to Resolve Common CORS Errors

What's Included in the Work

• Audit of current CORS configuration and problem identification—95% of issues are identified within 30 minutes.
• CORS setup on Nginx or Apache (depending on the environment).
• Implementation of dynamic CORS via PHP (if required).
• Development of a proxy server for Bitrix24 REST (if necessary).
• Testing of all scenarios (simple, preflight, with credentials)—an average of 8 test cases.
• Documentation and recommendations for ongoing support.

How to Configure CORS: Step-by-Step Guide

1. Determine the list of allowed origins.
2. Choose the configuration method: Nginx (static) or PHP (dynamic).
3. Add handling of OPTIONS requests with the required headers.
4. Set Access-Control-Allow-Credentials: true for requests with sessions.
5. Test via curl or browser developer tools.

Configuring CORS is 30 minutes of work with a proper understanding of the mechanism. Most CORS problems are solved by correct header placement (before outputting the response body) and proper handling of OPTIONS requests. If you want to avoid hours of debugging, entrust this task to professionals. Contact us to get a consultation for your project. We guarantee that after configuration, your API will work correctly with any browser clients.

1C-Bitrix Module Development and Setup

The main trap of Bitrix is init.php. You add an OnBeforeIBlockElementUpdate handler there, then another one — a year later the file is 2000 lines, and on every hit all that code executes. We move business logic into full-fledged modules with D7 ORM, custom tables, and administrative interface. The module can be disabled, transferred to another project, covered with tests — none of that is possible with init.php. Our team has 10+ years of Bitrix experience, certified specialists, and a 6-month code guarantee. Request a consultation — we'll explain how to migrate legacy code to a modular architecture.

Why is init.php the worst place for business logic?

Init.php does not support class autoloading, lacks an isolated namespace, cannot be unit tested, and cannot be disabled without editing the file itself. Every handler written there runs on every request, even if not needed. In a module, you register handlers through EventManager, and they only execute when the event occurs. Performance difference: up to 3x with 10+ handlers.

Standard Modules: Typical Problems and Solutions

Information blocks. IBlock architecture is the first thing we review on any project. A classic mistake: one catalog infoblock with 80 properties, 30 of which are multiple. The b_iblock_element_property table swells to millions of rows, and CIBlockElement::GetList with filtering on three properties does a full scan. We move reference data to Highload-blocks, eliminate multiple properties where possible, and design the structure for 5x growth.

e-Store (sale). Cart business rules are a separate story. We set discount priorities to prevent two campaigns from giving 60% instead of 30%, connect payment handlers, and write custom validation via OnSaleOrderBeforeSaved.

Search. The built-in search module with morphology works up to 10–15 thousand elements. Beyond that — Elasticsearch. We configure it via the Bitrix search module API, indexing through CSearchFullText or custom indexers.

Highload-blocks for dictionaries, logs, user data — instead of bloated IBlocks. Direct queries via Bitrix\Highloadblock\HighloadBlockTable, custom tables instead of the EAV structure of standard infoblocks. A million records — no degradation.

Mail events. Configuration is not just templates in b_event_message. The key is SPF, DKIM, DMARC on the DNS, otherwise transactional emails go to spam. We check deliverability and set up bounce handling.

How to Design Infoblocks for Performance?

We use Highload-blocks for reference data (colors, sizes, manufacturers) that are not involved in complex queries. For SKUs — a separate infoblock with linking via IBLOCK_ELEMENT_PROPERTY. Enable INDEX_PROPERTY for frequently filtered properties. Tagged caching: when an element changes, only the related cache is cleared. Highload-blocks process up to 10x faster than infoblocks with multiple properties on volumes of 100,000 records.

Custom Module Development

Each module follows the structure /local/modules/vendor.modulename/:

• install/index.php — setup class, create tables via $DB->RunSQLBatch()
• lib/ — D7 ORM classes, extending Bitrix\Main\ORM\Data\DataManager
• admin/ — administrative pages using CAdminList, CAdminForm
• include.php — autoloading, event handler registration via EventManager::getInstance()->registerEventHandler()
• REST API endpoints via \Bitrix\Rest\RestManager

The module registers in the system, appears in the "Installed Solutions" list, and has its own settings at /bitrix/admin/settings.php?mid=vendor.modulename. It can be enabled, disabled, and updated through UpdateSystem or custom migration mechanics.

Examples of implemented tasks:

• Campaign management — visual condition builder via CAdminCalendar, timers via agents (CAgent::AddAgent), analytics linked to the sale module
• Cost calculator — React widget on the frontend, REST API in the module, formulas stored in a Highload-block
• Booking system — real-time calendar, locking via $DB->StartTransaction() / $DB->Commit() on concurrent requests, integration with channel manager via webhook

Components and Composite Cache

Component customization via result_modifier.php and component_epilog.php, not by editing template.php of the standard template. This way core updates are painless.

Composite cache ("Composite Site" technology) — the server sends ready HTML, bypassing PHP routing. Dynamic areas (cart, authorization) are loaded via CBitrixComponent::setFrameMode(true) and AJAX. TTFB drops to 30–50 ms. But there are caveats: not all components are compatible, $APPLICATION->ShowPanel() breaks composite, and careful markup of <div id="bx-composite-..."> is required.

What to Check Before Installing a Marketplace Module?

Before installing a module from the marketplace, an audit is mandatory. We check: SQL queries without prepared statements (hello SQL injection), direct use of $_REQUEST without filtering, use of outdated kernel API instead of D7, conflicts with the composite cache module. A module with no updates for over a year and a few dozen installations is likely a problem on the next PHP update. A typical case: a module calls CIBlockElement::GetList with no cache reset — the site crashes with 5000 elements.

Migration to D7

When upgrading PHP or switching to a new edition — refactor outdated calls:

• CIBlockElement::GetList() → Bitrix\Iblock\Elements\ElementTable::getList()
• CSaleOrder::GetList() → Bitrix\Sale\Order::getList()
• CModule::IncludeModule() → Bitrix\Main\Loader::includeModule() Testing on staging, rollback via git on issues.

According to official 1C-Bitrix documentation, D7 ORM is the recommended tool for working with data, providing type safety and automatic query generation.

Comparison: Init.php vs Module

Module Development Scope and Cost

What is included in module development?

• Technical specification and architectural plan
• Code following PSR-4 and Bitrix code style
• Unit tests (PHPUnit) for business logic
• Integration tests for events and REST API
• Installation, configuration, and API documentation
• Repository and documentation access
• Administrator training for module usage
• 6-month warranty support

Estimated timelines and complexity:

Cost is calculated individually — contact us for a project estimate.

Module Testing

Unit tests via PHPUnit cover business logic: discount calculation, validation, document generation. Mocks for Bitrix\Main\Application::getConnection() allow tests to be DB-independent. Integration tests verify event handlers on a real database — OnAfterIBlockElementAdd, OnSaleOrderSaved, etc. REST API endpoints are tested via curl or PHPUnit HTTP client. Critical for modules working with b_sale_order, b_catalog_price — where errors cost money.

Compatibility is checked on PHP 7.4, 8.0, 8.1, 8.2 and editions: Standard, Small Business, Business. We check conflicts with popular marketplace modules — they often intercept the same events. Load testing: measurements on 10K, 100K, 1M records, profiling via Xdebug for memory leaks and N+1 queries.

Practical Examples

Campaign module for an electronics chain. The built-in sale module discounts did not cover scenarios like "2+1", a gift with purchase over a certain amount, or combined conditions. We built a visual builder: marketers create rules via drag-and-drop without development tickets. Campaign calendar, auto-deactivation via agents, analytics linked to b_sale_order — conversion, average check, usage count. Time to launch a new campaign dropped from two days to half an hour.

Calculator for builders. Parameters (area, materials, number of floors) → formula → preliminary estimate → lead to CRM via CRest::call('crm.lead.add'). Regional coefficients and seasonal markups from a Highload-block, material prices from 1C exchange. The number of target leads increased by a third: clients see a breakdown before calling a manager.

Booking for a hotel chain. Real-time availability via AJAX requests to a custom table vendor_booking_slots, seasonal tariff calculation, synchronization with Booking.com via channel manager API. Room locking on concurrent booking via SELECT ... FOR UPDATE in transactions. Timezones handled via \DateTimeZone — a guest from Vladivostok and a manager from Moscow see the same picture.

We will evaluate your project within one day. Write to us — we'll tell you what is included in turnkey development. Contact us for a consultation on your project. Order a custom module development — get a ready solution with documentation and support.