{"id":112743,"date":"2026-01-22T15:33:00","date_gmt":"2026-01-22T15:33:00","guid":{"rendered":"https:\/\/adjoe.io\/?post_type=glossary&#038;p=112743"},"modified":"2026-03-09T15:36:14","modified_gmt":"2026-03-09T15:36:14","slug":"idfa-identifier-for-advertisers","status":"publish","type":"glossary","link":"https:\/\/adjoe.io\/zh-tw\/glossary\/idfa-identifier-for-advertisers\/","title":{"rendered":"IDFA"},"content":{"rendered":"\n<div class=\"glossary-description\">\n\t\t<div class=\"glossary-description__wrapper\">\n              <h1 class=\"glossary-description__title\">\n          What is the Identifier for Advertisers: IDFA?\n        <\/h1>\n      \t\t\t<div class=\"glossary-description__icon\"><\/div>\n\t\t\t<div class=\"glossary-description__text\">\n\t\t\t\tThe identifier for advertisers (IDFA) is a unique device identifier that Apple assigns to each iOS device.\u00a0<br> <br> IDFA (or iOS device ID) enables advertisers to monitor user engagement, deliver personalized ads, &#038; track post-install activity.\n\t\t\t<\/div>\n\t\t<\/div>\n<\/div>\n\n\n\n<div style=\"height:27px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<div class=\"glossary-takeaways\">\n\t<div class=\"container\">\n\t\t<div class=\"glossary-takeaways__wrapper\">\n\t\t\t<div class=\"glossary-takeaways__title\">\n\t\t\t\tKey Takeaways\u00a0\n\t\t\t<\/div>\n\t\t\t<div class=\"glossary-takeaways__text\">\n\t\t\t\t<ul>\n<li>IDFA is a <strong>unique device identifier for iOS<\/strong> used to <strong>measure ad performance<\/strong> &amp; user behavior, similar to a third-party cookie on a web browser.<\/li>\n<li>With the iOS 14.5 rollout and the App Tracking Transparency (ATT), tracking requires <strong>explicit user consent<\/strong>. Opt-in rates now reach 50% globally.<\/li>\n<li>Without automatic IDFA data, advertisers rely on <strong>SKAdNetwork<\/strong>, AdAttributionKit, and probabilistic models for attribution.<\/li>\n<\/ul>\n\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n<\/div>\n\n\n\n<div style=\"height:51px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">What is IDFA Used For?<\/h2>\n\n\n\n<p>Advertisers use IDFA data to measure ad performance, optimize campaigns, and perform data-driven user acquisition strategies.<\/p>\n\n\n\n<p>When an ad network supports IDFA tracking and the advertiser records ad interactions, the IDFA can let you see which users clicked an ad.&nbsp;<\/p>\n\n\n\n<div style=\"height:31px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"652\" src=\"https:\/\/adjoe.io\/app\/uploads\/2025\/09\/IDFA-1-1024x652.jpg\" alt=\"What is IDFA? IDFA adtech glossary.\nWhat is the Identifier for Advertisers (IDFA)? adjoe blog  \" class=\"wp-image-112798\" srcset=\"https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-1-1024x652.jpg 1024w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-1-300x191.jpg 300w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-1-768x489.jpg 768w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-1-1536x979.jpg 1536w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-1-2048x1305.jpg 2048w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<div style=\"height:48px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>Users can turn off such tracking to manually reset or disable it, or turn on Limit Ad Tracking (LAT). Limit Ad Tracking is an iOS feature that allows users to opt out of sharing their data.&nbsp;<\/p>\n\n\n\n<p>When this setting is on, the user\u2019s IDFA is hidden (shown as zeros), so ad networks can\u2019t track the device or show personalized ads.&nbsp;<\/p>\n\n\n\n<p>The Android equivalent of IDFA is the <a href=\"https:\/\/adjoe.io\/glossary\/gaid-google-advertising-id\/\" target=\"_blank\" rel=\"noreferrer noopener\">Google Advertising ID<\/a> (GAID). Users can also reset their GAID to opt out of personalization on their Android devices.&nbsp;<\/p>\n\n\n\n<div style=\"height:51px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">IDFA Affected by iOS 14.5 &amp; App Tracking Transparency (ATT)&nbsp;&nbsp;<\/h2>\n\n\n\n<p>Back in 2021, Apple flipped the switch on how tracking works in <a href=\"https:\/\/adjoe.io\/glossary\/in-app-advertising\/\" target=\"_blank\" rel=\"noreferrer noopener\">mobile app advertising<\/a>.&nbsp;<\/p>\n\n\n\n<p>With iOS 14.5, Apple introduced App Tracking Transparency (ATT), and apps could no longer access the IDFA automatically.&nbsp;<\/p>\n\n\n\n<p>Instead, users now get a pop-up: \u201cAllow this app to track your activity?\u201d With this update, advertisers lost the ability to follow users across apps unless they <strong>opted in<\/strong>.<\/p>\n\n\n\n<div style=\"height:41px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"869\" height=\"1024\" src=\"https:\/\/adjoe.io\/app\/uploads\/2025\/09\/IDFA-02-869x1024.jpg\" alt=\"IDFA Affected by iOS 14.5 &amp; App Tracking Transparency (ATT)\u00a0\u00a0- What is the Identifier for Advertisers (IDFA)?\nWhat is IDFA?\" class=\"wp-image-112884\" srcset=\"https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-02-869x1024.jpg 869w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-02-255x300.jpg 255w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-02-768x905.jpg 768w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-02-1303x1536.jpg 1303w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-02-1738x2048.jpg 1738w\" sizes=\"auto, (max-width: 869px) 100vw, 869px\" \/><\/figure>\n\n\n\n<div style=\"height:22px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Impact of ATT on IDFA Opt-in Rates<\/h2>\n\n\n\n<div style=\"height:12px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>A <a href=\"https:\/\/www.singular.net\/blog\/att-opt-in-rates-2024\/\">recent Singular study<\/a> shows ATT opt-in rates dropped from 26% in 2021 to under 14% in mid-2024.&nbsp;<\/p>\n\n\n\n<p>But there\u2019s hopeful news for advertisers. Globally, <a href=\"https:\/\/www.appsflyer.com\/company\/newsroom\/pr\/post-att-growth\/\">50% of users<\/a> consent to tracking in 2025, a 10% increase since ATT\u2019s initial rollout.<\/p>\n\n\n\n<p>Games see higher opt-ins than other apps (about 19% vs. 12%), but results vary by category. Weather apps can reach 40%, while News and Medical are often below 5%.&nbsp;<\/p>\n\n\n\n<p>If the user does not consent to allow IDFA tracking, the only way to perform attribution for iOS campaigns is with Apple\u2019s SKAdNetwork (SKAN) and\/or AdAttributionKit.<\/p>\n\n\n\n<div style=\"height:49px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"836\" src=\"https:\/\/adjoe.io\/app\/uploads\/2025\/09\/IDFA-03-1024x836.jpg\" alt=\"Impact of ATT on IDFA Opt-in Rates\n\nApp Tracking transparency - ATT User Consent Flow \" class=\"wp-image-112854\" srcset=\"https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-03-1024x836.jpg 1024w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-03-300x245.jpg 300w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-03-768x627.jpg 768w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-03-1536x1254.jpg 1536w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA-03-2048x1673.jpg 2048w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<div style=\"height:55px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>One effective way to increase opt-in rates is through thoughtful onboarding. For example, adjoe\u2019s <a href=\"https:\/\/adjoe.io\/solutions\/monetize-your-app\/playtime\/\">Playtime ad format<\/a> addresses the challenge by guiding users step by step.&nbsp;<\/p>\n\n\n\n<p>It clearly communicates the value exchange and reframes \u2018tracking\u2019 as \u2018personalization.\u2019 This level of transparency builds trust and has proven results, driving <a href=\"https:\/\/adjoe.io\/blog\/everything-you-need-to-know-about-adjoe-user-opt-in\/\">opt-in rates up to 70%<\/a>, far above the industry average.&nbsp;&nbsp;&nbsp;&nbsp;<\/p>\n\n\n\n<div style=\"height:42px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"836\" src=\"https:\/\/adjoe.io\/app\/uploads\/2025\/09\/IDFA4-1024x836.jpg\" alt=\"adjoe Playtime personalized opt-in for tracking IDFA\n\n- How Playtime helps in increasing Opt-ins. What is the Identifier for Advertisers (IDFA)?\" class=\"wp-image-112804\" srcset=\"https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA4-1024x836.jpg 1024w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA4-300x245.jpg 300w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA4-768x627.jpg 768w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA4-1536x1254.jpg 1536w, https:\/\/adjoe.io\/wp-content\/uploads\/2025\/09\/IDFA4-2048x1673.jpg 2048w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<div style=\"height:32px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">IDFA Impact on Advertisers&nbsp;<\/h2>\n\n\n\n<p>Without IDFA, advertisers lose much of the targeting precision they once had.&nbsp;<\/p>\n\n\n\n<p>Tracking ad performance and user behavior has become much harder. You cannot identify and retarget users individually, unless they opt in to IDFA.&nbsp;<\/p>\n\n\n\n<p>Advertisers struggle to measure <a href=\"https:\/\/adjoe.io\/glossary\/app-lifetime-value-ltv\/\">LTV<\/a>, ROI, and user actions with limited detail and accuracy in SKAdNetwork (SKAN). Conversion tracking can be delayed (at least 24 hours after install), making campaign optimization harder.<\/p>\n\n\n\n<p>SKAdNetwork\u2019s limitations have led to a rise in ad fraud due to fewer anti-fraud signals and reduced transparency.<\/p>\n\n\n\n<div style=\"height:42px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Future of App Advertising in the Post-IDFA World&nbsp;<\/h2>\n\n\n\n<p>SKAdNetwork (and Apple\u2019s new AdAttributionKit) dominate privacy\u2011safe attribution, offering aggregated, anonymous campaign insights via <a href=\"https:\/\/adjoe.io\/glossary\/what-is-postback\/\">postbacks<\/a> rather than device IDs.<\/p>\n\n\n\n<p>There\u2019s a shift towards AI\u2011powered contextual advertising, first-party data, and server-side measurement.&nbsp;<\/p>\n\n\n\n<p>App marketers are increasingly using <a href=\"https:\/\/adjoe.io\/blog\/programmatic-bidding-for-mobile-in-app-advertising\/\">incrementality testing<\/a>, media mix modeling, and engagement-based attribution (e.g., session length, retention rate). It helps evaluate <a href=\"https:\/\/adjoe.io\/blog\/programmatic-advertising-kpis\/\">campaign performance<\/a> without relying on granular tracking.<\/p>\n\n\n\n<p>MMPs originally relied on IDFA for device-level attribution. But now they enable privacy-first measurement by aggregating SKAdNetwork postbacks from Apple and <a href=\"https:\/\/adjoe.io\/glossary\/mobile-ad-networks\/\">ad networks<\/a>.&nbsp;<\/p>\n\n\n\n<p>They are also applying probabilistic models when deterministic data is unavailable.<\/p>\n\n\n\n<div style=\"height:42px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">FAQs<\/h2>\n\n\n\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-1757427700450\"><strong class=\"schema-faq-question\"><strong>What does IDFA mean?<\/strong><br\/><\/strong> <p class=\"schema-faq-answer\">IDFA (Identifier for Advertisers) is a unique device identifier on iOS devices. It helps advertisers perform attribution and track app installs while respecting user privacy.\u00a0<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1757427729691\"><strong class=\"schema-faq-question\"><br\/><strong>What is an example of IDFA?<\/strong><br\/><\/strong> <p class=\"schema-faq-answer\">An alpha-numeric string like AEBE52E7-03EE-455A-B3C4-E57283966239 is an example of an IDFA. It links user actions to ads without revealing personal info.<br\/><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1757427739901\"><strong class=\"schema-faq-question\"><br\/><strong>How do I find my IDFA number?<\/strong><br\/><\/strong> <p class=\"schema-faq-answer\">On iOS 14+ devices, go to Settings > Privacy > Tracking > Allow Apps to Request to Track. Your IDFA is accessible if users opted into tracking.<br\/><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1757427748755\"><strong class=\"schema-faq-question\"><br\/><strong>What challenges do advertisers face with limited access to IDFA?<\/strong><br\/><\/strong> <p class=\"schema-faq-answer\">With iOS 14.5+ and ATT opt-in, many users opt out of IDFA tracking. This limits attribution, reduces ad targeting precision, and complicates reporting for mobile measurement partners.<br\/><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1757427756407\"><strong class=\"schema-faq-question\"><br><strong>Is IDFA still used in 2026?<\/strong><br><\/strong> <p class=\"schema-faq-answer\">Yes, IDFA is still used when users opt in. For opt-out users, advertisers rely on device identifiers, Google Advertising ID, and other post-IDFA solutions to accurately attribute installs and transactions.<br\/><\/p> <\/div> <\/div>\n\n\n\n<p><\/p>\n","protected":false},"author":57,"featured_media":112793,"menu_order":0,"template":"","ppma_author":[185],"class_list":["post-112743","glossary","type-glossary","status-publish","has-post-thumbnail","hentry"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.1.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>What is IDFA? 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