媒体报道

解读移动广告 ID（MAID）原文标题：Explaining mobile advertising ID

发表时间：2026-09-26采集时间：2026-10-09 10:35:00来源：ppc.land原文语言：en状态：完整

原始链接：https://ppc.land/mobile-advertising-id

内容概要总结

本文是 PPC Land 对移动广告 ID（MAID）的深度解读。MAID 是手机操作系统分配给设备的随机字符串，iOS 上为 IDFA，Android 上为 GAID/AAID，用于让 App 在无共享 cookie 的前提下实现定向、频次控制与安装归因。文章说明其流转链路：App/SDK 通过 ASIdentifierManager（iOS）或 AdvertisingIdClient（Android）读取，SSP 复制进 OpenRTB 的 ifa 字段，DSP 再与受众细分、频次计数器、转化日志比对。文章梳理从 UDID、Android ID、IMEI、MAC 到 IDFA（iOS 6，2012 年 9 月）、Android 广告 ID（2013 年 10 月）、iOS 14.5 ATT（2021 年 4 月 26 日生效）的演变，并给出大量关键数据：可追踪美国用户比例从 72.6% 降至 17.9%、Meta 称 iOS 变化影响约 100 亿美元、2026 年 Q1 ATT 平均同意率 38%、FTC 对 Kochava/Mobilewalla 的执法、法意德对 Apple 的反垄断处罚、Google 2025 年 10 月退出 Android Privacy Sandbox。文末给出完整时间线。

翻译内容

原文内容（English）

⚠ 说明：已剔除文末“Related PPC Land coverage”“Read Next”等站内推荐位，保留文章主体（含时间线与摘要）。为与原文结构对齐，已补回原文的 Related PPC Land coverage / Read Next / Discussion 章节及其标题与图片占位符。

移动广告 ID（mobile advertising ID，常缩写为 MAID）是手机操作系统分配给设备的一串随机字符串，以便 App 以及在其中运作的广告公司能够识别该设备，用于定向投放、频次控制和衡量。Apple 的版本称为 Identifier for Advertisers（IDFA）。Google 的版本称为 advertising ID，通常写作 GAID 或 AAID。之所以需要这个标识符，是因为 App 与网页不同，它们不共享 cookie 存储。每个 App 都运行在自己的沙箱中，如果没有一个公共值，广告网络就无法判断那个在益智游戏里看到广告的人后来安装了某零售商的 App。在 MAID 出现之前，业界用永久性设备标识来弥合这一鸿沟，而用户既无法重置也无法拒绝这些标识。

标识符如何流转

两个平台都将该值格式化为通用唯一标识符（UUID）：32 个十六进制字符，分为五个用连字符分隔的组。App 或嵌入其中的软件开发工具包（SDK）通过操作系统调用读取该值——iOS 上是 ASIdentifierManager，Android 上是 AdvertisingIdClient。设备上的每个 App 都会收到相同的字符串。来自广告网络、中介平台和衡量公司的追踪 SDK 会把它连同设备与事件数据一起采集。

该值可以随时被重置，并且自 Android 12 起可以被彻底删除。在 iOS 14.5 及更高版本上，App 必须先通过 App Tracking Transparency（ATT）弹窗请求许可。当用户拒绝、删除该 ID 或选择退出个性化时，系统会交给 App 一串零。据 Android 开发者文档，以 Android 13 为目标的应用还必须在清单中声明 AD_ID 权限，否则广告 ID“会被自动移除并替换为一串零”。

在竞价中，供应方平台（SSP）会把该值复制到 OpenRTB 设备对象的 ifa 字段中。规范将其定义为“获准供广告主以明文使用的 ID（即未哈希）”，并期望它“来自对设备操作系统所提供的广告 API 的调用”。与之相邻的是 lmt，即限制广告追踪标志，其中 1 表示“必须按商业准则限制追踪”。IAB Tech Lab 的 iOS 14 指引新增了 device.ext.atts，以 0（未确定）、1（受限）、2（拒绝）或 3（已授权）承载 ATT 状态，并告知卖方除非状态为 3，否则应将 lmt 设为 1。

在买方，需求方平台（DSP）会将该值与受众细分、频次计数器和转化日志进行比对。移动衡量合作伙伴（MMP）历史上通过在两个事件上找到同一个标识符来把点击与安装进行匹配。广告主还会上传 MAID 列表作为自定义受众。

联网电视（CTV）平台会发放各自的等价标识符，例如 Roku 和 Amazon Fire TV 的。IAB Tech Lab 针对 OTT（over-the-top）平台的指南于 2018 年 4 月 3 日发布草案、同年 12 月定稿，要求此类 ID 可重置、与硬件标识符分离，并附带一个限制广告追踪信号。当一个电视上的该标识符出现在竞价请求中时，Display & Video 360 会在该电视上的各个 App 之间限制频次。

从硬件序列号到同意弹窗

早期移动广告使用设备暴露的一切。在 iOS 上那是唯一设备标识符（UDID）；在 Android 上是 Android ID、IMEI 或 MAC 地址。OpenRTB 在 didsha1、dpidmd5 和 macsha1 等字段中承载哈希版本，这些字段在 2.6 版中全部被弃用。

Apple 于 2012 年 9 月随 iOS 6 引入 IDFA，并附带一个 Limit Ad Tracking 开关。2013 年 3 月 21 日，它告知开发者：从 5 月 1 日起 App Store 将不再接受访问 UDID 的新 App 或更新。Google 于 2013 年 10 月 31 日跟进，Google Play services 4.0 新增了“一个用于广告目的的新匿名标识符（用于替代 Android ID）”，合规期限为 2014 年 8 月。Google Play 政策至今仍禁止在未经明确同意的情况下将其与持久标识符关联。自 2016 年的 iOS 10 起，开启 Limit Ad Tracking 的设备会返回零。

Apple 于 2020 年 6 月 22 日宣布 ATT，9 月 3 日推迟，并于 2021 年 4 月 26 日随 iOS 14.5 强制执行。Apple 将追踪定义为：为定向广告或衡量而将来自某 App 的数据与来自“其他公司的 App、网站或线下资产”的数据相关联，或将其与数据经纪商共享。零成为默认值；用户必须点击“允许”才能改变这一点。

Google 采取了更温和的路线。它于 2021 年 7 月 28 日宣布，选择退出的用户将收到零，先从 2021 年底的 Android 12 设备开始，并从 2022 年 4 月 1 日起扩展到所有 Play 设备。面向儿童的应用可能完全不得传输该 ID。2022 年 2 月 16 日，Google 负责 Privacy Sandbox 的副总裁 Anthony Chavez 表示，Android 将转向“无需跨 App 标识符（包括广告 ID）即可运作”的解决方案，并对现有功能“至少支持两年”。该计划未能延续。据其 Privacy Sandbox 博客，Google 于 2025 年 10 月 17 日在 Android 上退出了 Topics、Protected Audience、Attribution Reporting 和 SDK Runtime。广告 ID 仍在服务中。

为什么重要

对大多数 App 内广告而言，MAID 是那个连接键（join key）。电子隐私信息中心（EPIC）与爱尔兰公民自由委员会（ICCL）Enforce 部门于 2025 年 1 月提交的一份投诉称，Google 的实时竞价系统触达了 91% 的 Android App 和 75% 的 iOS App，MAID 正是其所广播的标识符之一。

ATT 展示了失去这个键的代价。Kraft 及其同事的研究（被经济学家 Reinhold Kesler 在 2026 年的一项研究中引用）估计，可追踪美国用户的比例从 72.6% 下降到 17.9%。据 CNBC 报道，Meta 首席财务官 Dave Wehner 于 2022 年 2 月 2 日告诉投资者，iOS 变化对该年的影响“约为 100 亿美元”。iOS 上的归因转向了 SKAdNetwork，它能在不识别设备的情况下确认一次安装。Android 保留了确定性匹配，因此如今一次投放活动要在两套衡量体系下运行。

此后同意率略有上升。其业务依赖归因的衡量公司 Adjust 给出的 2026 年第一季度平均 ATT 同意率为 38%，高于一年前的 35%。

局限与争议

MAID 是假名的（pseudonymous），不是匿名的。欧洲法律将假名化数据视为个人数据，而美国的执法者也已表明这个标签多么容易失效。在其 2022 年 8 月针对 Kochava 的投诉中，联邦贸易委员会（FTC）称，一份将 MAID 与 GPS 坐标配对的数据集样本覆盖了 6100 万台唯一设备，并使其“有可能识别出曾到访某女性生殖健康诊所的移动设备，并将该移动设备追踪到单一住宅”。2024 年 12 月，该机构称 Mobilewalla 在 2018 年 1 月至 2020 年 6 月期间收集了超过 5 亿个与精确位置配对的广告标识符，其中部分来自其输掉的竞价中的竞价请求。2026 年 5 月，有报道称以色列公司推销将广告标识符与 Starlink 终端关联的系统；其中一家声称已对约 20 万个去匿名化。

ATT 本身在竞争法层面存在争议。法国竞争管理局于 2025 年 3 月对 Apple 罚款 1.5 亿欧元，认定其设计让用户需要两次同意才能被追踪、却只需一次拒绝即可。意大利监管机构随后于 2025 年 12 月 22 日罚款 9860 万欧元。德国联邦卡特尔局认定，Apple 并未将 IDFA 用于自身广告，而是通过一个单独的、引导用户同意的弹窗来征求同意；2026 年 8 月 13 日，该局接受了 Apple 重新设计 ATT 弹窗的承诺，而非处以罚款。其主席 Andreas Mundt 表示，目的“明确不是”最大化同意率。Apple 表示该弹窗对所有开发者（包括它自己）都是一致的，并援引消费者、隐私倡导者和数据保护机构的“强烈支持”。

限制该 ID 也把数据收集推向了别处。Kesler 发现，在存活的 App 中，披露与用户关联的数据的占比到 2025 年从 10.4% 升至 24.1%。法国数据保护监管机构 CNIL 于 2022 年 12 月 29 日对游戏发行商 Voodoo 罚款 300 万欧元，原因是其在用户拒绝 ATT 后仍读取供应商标识符（IDFV）用于广告。

不等于

供应商标识符与应用集 ID。IDFV 只在一个开发者的设备内各 App 之间共享，且不需要 ATT 许可，但它不得与其他数据结合来追踪用户。Google 的 app set ID 在一个 Play 开发者账户内服务于分析和反欺诈，并在 13 个月未使用后重置。

硬件标识符。IMEI 号码、序列号、MAC 地址和 UDID 无法重置。Android 10 阻止了大多数 App 读取 IMEI 和序列号。

App bundle ID。bundle 命名的是应用，而非设备，且不携带用户信息。

近期进展

法院和监管机构正在收窄该 ID 可以流转的范围。Google 实时竞价和解案于 2026 年 3 月 26 日获批，要求提供一项用户控制功能，从竞价请求中剥离设备广告 ID。FTC 于 2026 年 5 月以一项命令了结了 Kochava 案，该命令将 MAID 与 IDFA 结合位置信号的情形计为精确位置数据。加州面向数据经纪商的删除平台于 2026 年 1 月 1 日上线，但截至 2 月 27 日，只有 10% 的请求携带了移动广告 ID；自 8 月 1 日起，经纪商必须至少每 45 天检查一次。

需求并未消退。OpenAI 于 2026 年 8 月 31 日开始接受 Google Advertising ID 用于 ChatGPT 自定义受众。2026 年 9 月 16 日，Apple 为德国、法国、意大利、波兰和罗马尼亚发布了一版重新设计的 ATT 弹窗，去掉了“track”一词，并将“Ask App Not to Track”改标为“Reject”。

时间线

2012 年 9 月：Apple 随 iOS 6 引入 IDFA 和 Limit Ad Tracking
2013 年 3 月 21 日：Apple 宣布自 5 月 1 日起 App Store 将拒绝访问 UDID 的应用
2013 年 10 月 31 日：Google Play services 4.0 引入 Android 广告 ID
2014 年 8 月：Android 应用在广告中使用广告 ID 替代其他设备标识符的截止期限
2016 年 9 月：iOS 10 在启用 Limit Ad Tracking 时返回零
2018 年 4 月 3 日：IAB Tech Lab 发布 OTT 平台广告标识符指南草案
2018 年 12 月：IAB Tech Lab 定稿 OTT 标识符指南
2020 年 6 月 22 日：Apple 宣布 App Tracking Transparency
2020 年 9 月 3 日：Apple 推迟 ATT 强制执行
2021 年 4 月 26 日：ATT 随 iOS 14.5 生效
2021 年 7 月 28 日：Google 宣布选择退出的 Android 用户将收到零
2022 年 2 月 2 日：Meta 将 iOS 变化 2022 年的影响估计为约 100 亿美元
2022 年 2 月 16 日：Google 宣布 Android 上的 Privacy Sandbox 并计划超越广告 ID
2022 年 4 月 1 日：归零的广告 ID 扩展到所有支持 Google Play 的设备
2022 年 8 月：FTC 就与 MAID 关联的位置数据起诉 Kochava
2022 年 12 月 29 日：CNIL 就广告中使用 IDFV 对 Voodoo 罚款 300 万欧元
2024 年 12 月 3 日：FTC 就位置数据对 Mobilewalla 和 Gravy Analytics 采取行动
2025 年 1 月 16 日：EPIC 与 ICCL Enforce 就 Google 实时竞价数据提起 FTC 投诉
2025 年 3 月：法国就 ATT 对 Apple 罚款 1.5 亿欧元
2025 年 10 月 17 日：Google 在 Android 和 Chrome 上退出 Privacy Sandbox 技术
2025 年 12 月 22 日：意大利就 ATT 对 Apple 罚款 9860 万欧元
2026 年 1 月 1 日：加州数据经纪商删除平台上线
2026 年 3 月 26 日：Google RTB 和解案最终获批，要求提供剥离设备广告 ID 的控制功能
2026 年 5 月：FTC 以同意令了结 Kochava 案
2026 年 8 月 13 日：Bundeskartellamt 接受 Apple 重新设计 ATT 弹窗的承诺
2026 年 8 月 31 日：ChatGPT 广告开始接受 Google Advertising ID 用于自定义受众
2026 年 9 月 16 日：Apple 为五个欧盟国家发布重新设计的 ATT 弹窗

摘要

谁。 Apple 和 Google 在 iOS 和 Android 上发放这些标识符，Roku、Amazon 及其他电视平台在 CTV 上亦然。应用开发者及其 SDK 读取它们；SSP 将它们传给 DSP；衡量合作伙伴、数据经纪商和广告主使用它们。IAB Tech Lab 定义它们如何流转，美国和欧洲的竞争与隐私监管机构设定边界。

什么。 移动广告 ID 是操作系统出于广告目的向设备上每个 App 暴露的一个随机、用户可重置的 UUID。它在 OpenRTB 竞价请求的 ifa 字段中流转，并在用户拒绝、删除或退出时以一串零返回。

何时。 Apple 于 2012 年 9 月引入 IDFA，Google 于 2013 年 10 月引入其广告 ID，二者都取代了永久性设备标识符。Apple 于 2021 年 4 月 26 日通过 ATT 将访问变为需主动选择加入；Google 从 2021 年底起对选择退出的用户将该 ID 归零，并在 2025 年 10 月放弃了本用以取代它的 Android Privacy Sandbox API。

何地。 它在手机和平板上的移动 App 内运作，并通过平台等价物在联网电视和流媒体设备上运作。它不存在于网页浏览器中，那里由 cookie 承担同样角色。

为什么。 App 之间不共享 cookie，因此广告主需要一个公共值来跨 App 定向、限制频次和归因安装。正是让它对广告有用的那种持久性，让数据经纪商和其他人能够把设备的移动轨迹与某个人关联起来，这也是平台、监管机构和法院持续限制它的原因。

作者：Luis Rijo（PPC Land 创始人，自 2016 年起每日撰写，逾 10,000 篇文章，由读者资助，无赞助内容）。

Luís Rijo 自 2016 年创办 PPC Land 以来每日撰写。逾 10,000 篇文章，由读者资助，无赞助内容。线索与更正：luis@ppc.land

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讨论

A mobile advertising ID, often shortened to MAID, is a random string that a phone's operating system assigns to the device so that apps, and the advertising companies working inside them, can recognise it for targeting, frequency capping and measurement. Apple's version is the Identifier for Advertisers (IDFA). Google's is the advertising ID, usually written GAID or AAID. The identifier exists because apps, unlike web pages, share no cookie jar. Each runs in its own sandbox, and without a common value an ad network cannot tell that the person who saw an ad in a puzzle game later installed a retailer's app. Before MAIDs, the industry bridged that gap with permanent device identifiers that users could neither reset nor refuse.

How the identifier moves

Both platforms format the value as a universally unique identifier (UUID): 32 hexadecimal characters in five hyphenated groups. An app, or a software development kit (SDK) embedded in it, reads the value through an operating system call, ASIdentifierManager on iOS and AdvertisingIdClient on Android. Every app on the device receives the same string. Tracking SDKs from ad networks, mediation platforms and measurement firms collect it alongside device and event data.

The value can be reset at any time, and since Android 12 it can be deleted outright. On iOS 14.5 and later, an app must first ask permission through the App Tracking Transparency (ATT) prompt. Where a user refuses, deletes the ID or opts out of personalisation, the system hands the app a string of zeros instead. Apps targeting Android 13 must also declare the AD_ID permission in their manifest, or the advertising ID "is automatically removed and replaced with a string of zeroes", according to Android developer documentation.

In auctions, a supply-side platform (SSP) copies the value into the ifa field of the OpenRTB device object. The specification defines it as an "ID sanctioned for advertiser use in the clear (i.e., not hashed)", expected to be "derived from a call to an advertising API provided by the device's Operating System". Beside it sits lmt, the limit ad tracking flag, where 1 means "tracking must be limited per commercial guidelines". IAB Tech Lab's iOS 14 guidance added device.ext.atts, carrying the ATT status as 0 (not determined), 1 (restricted), 2 (denied) or 3 (authorised), and told sellers to set lmt to 1 unless the status is 3.

On the buy side, a demand-side platform (DSP) checks the value against audience segments, frequency counters and conversion logs. Mobile measurement partners historically matched a click to an install by finding the same identifier on both events. Advertisers also upload MAID lists as custom audiences.

Connected television (CTV) platforms issue their own equivalents, such as Roku's and Amazon Fire TV's. IAB Tech Lab's guidelines for over-the-top (OTT) platforms, released in draft on April 3, 2018 and finalised that December, require such IDs to be resettable, separate from hardware identifiers and accompanied by a limit ad tracking signal. Display & Video 360 caps frequency across apps on one television when that identifier appears in the bid request.

From hardware serials to consent prompts

Early mobile advertising used whatever the device exposed. On iOS that was the unique device identifier (UDID); on Android, the Android ID, the IMEI or the MAC address. OpenRTB carried hashed versions in fields such as didsha1, dpidmd5 and macsha1, all deprecated in version 2.6.

Apple introduced the IDFA with iOS 6 in September 2012, alongside a Limit Ad Tracking switch. On March 21, 2013, it told developers that from May 1 the App Store would no longer accept new apps or updates that accessed UDIDs. Google followed on October 31, 2013, when Google Play services 4.0 added "a new, anonymous identifier for advertising purposes (to be used in place of Android ID)", with compliance expected by August 2014. Google Play policy still bars linking it to persistent identifiers without explicit consent. From iOS 10 in 2016, a device with Limit Ad Tracking switched on returned zeros.

Apple announced ATT on June 22, 2020, postponed it on September 3 and enforced it with iOS 14.5 on April 26, 2021. Apple defines tracking as linking data from an app with data from "other companies' apps, websites, or offline properties" for targeted advertising or measurement, or sharing it with data brokers. Zeros became the default; a user had to tap "Allow" to change that.

Google took a softer route. It announced on July 28, 2021 that opted-out users would receive zeros, starting with Android 12 devices in late 2021 and extending to all Play devices from April 1, 2022. Apps aimed at children may not transmit the ID at all. On February 16, 2022, Anthony Chavez, Google's vice president for Privacy Sandbox, said Android would move to solutions that "operate without cross-app identifiers, including advertising ID", with existing features supported "for at least two years". That plan did not survive. On October 17, 2025, Google retired Topics, Protected Audience, Attribution Reporting and the SDK Runtime on Android, according to its Privacy Sandbox blog. The advertising ID remains in service.

Why it matters

For most in-app advertising, the MAID is the join key. A January 2025 complaint by the Electronic Privacy Information Center and the Irish Council for Civil Liberties' Enforce unit said Google's real-time bidding system reached 91% of Android apps and 75% of iOS apps, with MAIDs among the identifiers it broadcast.

ATT showed what losing that key costs. Research by Kraft and colleagues, cited in a 2026 study by economist Reinhold Kesler, estimated that the share of trackable US users fell from 72.6% to 17.9%. Meta's chief financial officer, Dave Wehner, told investors on February 2, 2022 that the impact of iOS changes was "on the order of $10 billion" for that year, according to CNBC. Attribution on iOS moved to SKAdNetwork, which confirms an install without identifying the device. Android kept deterministic matching, so a single campaign now runs under two measurement regimes.

Consent has since edged up. Adjust, a measurement firm whose business depends on attribution, put the average ATT opt-in rate at 38% in the first quarter of 2026, up from 35% a year earlier.

Limitations and disputes

A MAID is pseudonymous, not anonymous. European law treats pseudonymised data as personal data, and American enforcers have shown how easily the label fails. In its August 2022 complaint against Kochava, the Federal Trade Commission (FTC) said a sample dataset pairing MAIDs with GPS coordinates covered 61 million unique devices and made it "possible to identify a mobile device that visited a women's reproductive health clinic and trace that mobile device to a single family residence". In December 2024 the agency said Mobilewalla had collected more than 500 million advertising identifiers paired with precise location between January 2018 and June 2020, partly from bid requests in auctions it lost. In May 2026, Israeli firms were reported to market systems linking advertising identifiers to Starlink terminals; one claimed to have deanonymised about 200,000.

ATT itself is contested on competition grounds. France's competition authority fined Apple 150 million euros in March 2025, finding that the design made users consent twice to be tracked but refuse only once. Italy's authority followed with 98.6 million euros on December 22, 2025. Germany's Bundeskartellamt found that Apple does not use the IDFA for its own advertising, seeking consent through a separate prompt that steered users towards agreeing; on August 13, 2026 it accepted commitments to redesign the ATT prompt rather than impose a fine. Andreas Mundt, its president, said the aim was "expressly not" to maximise consent. Apple has said the prompt is consistent for all developers, including itself, and cited "strong support" from consumers, privacy advocates and data protection authorities.

Restricting the ID also pushed data collection elsewhere. Among surviving apps, Kesler found, the share disclosing data linked to users rose from 10.4% to 24.1% by 2025. France's data protection regulator, CNIL, fined game publisher Voodoo 3 million euros on December 29, 2022 for reading the identifier for vendors (IDFV) for advertising after users had refused ATT.

Not the same as

Identifier for vendors and app set ID. The IDFV is shared only across one developer's apps on a device and needs no ATT permission, but it may not be combined with other data to follow users. Google's app set ID serves analytics and fraud prevention within one Play developer account and resets after 13 months without use.

Hardware identifiers. IMEI numbers, serial numbers, MAC addresses and UDIDs cannot be reset. Android 10 blocked most apps from reading IMEI and serial numbers.

App bundle ID. The bundle names the application, not the device, and carries no user information.

Recent developments

Courts and regulators are narrowing where the ID may travel. The Google real-time bidding settlement, approved on March 26, 2026, requires a user control that strips device advertising IDs from bid requests. The FTC closed its Kochava case in May 2026 with an order that counts MAIDs and IDFAs combined with location signals as precise location data. California's deletion platform for data brokers went live on January 1, 2026, yet by February 27 only 10% of requests carried a mobile advertising ID; since August 1 brokers have had to check it at least every 45 days.

Demand has not faded. OpenAI began accepting the Google Advertising ID for ChatGPT custom audiences on August 31, 2026. On September 16, Apple published a redesigned ATT prompt for Germany, France, Italy, Poland and Romania that drops the word "track" and relabels "Ask App Not to Track" as "Reject".

Timeline

September 2012: Apple introduces the IDFA and Limit Ad Tracking with iOS 6

March 21, 2013: Apple announces that from May 1 the App Store will reject apps accessing UDIDs

October 31, 2013: Google Play services 4.0 introduces the Android advertising ID

August 2014: Deadline for Android apps to use the advertising ID in place of other device identifiers for ads

September 2016: iOS 10 returns zeros when Limit Ad Tracking is enabled

April 3, 2018: IAB Tech Lab releases draft guidelines for advertising identifiers on OTT platforms

December 2018: IAB Tech Lab finalises the OTT identifier guidelines

June 22, 2020: Apple announces App Tracking Transparency

September 3, 2020: Apple postpones ATT enforcement

April 26, 2021: ATT takes effect with iOS 14.5

July 28, 2021: Google announces that opted-out Android users will receive zeros

February 2, 2022: Meta puts the 2022 impact of iOS changes at about $10 billion

February 16, 2022: Google announces Privacy Sandbox on Android and plans to move beyond the advertising ID

April 1, 2022: Zeroed advertising IDs extend to all devices supporting Google Play

August 2022: FTC sues Kochava over location data tied to MAIDs

December 29, 2022: CNIL fines Voodoo 3 million euros over advertising use of the IDFV

December 3, 2024: FTC acts against Mobilewalla and Gravy Analytics over location data

January 16, 2025: EPIC and ICCL Enforce file an FTC complaint over Google's real-time bidding data

March 2025: France fines Apple 150 million euros over ATT

October 17, 2025: Google retires Privacy Sandbox technologies on Android and Chrome

December 22, 2025: Italy fines Apple 98.6 million euros over ATT

January 1, 2026: California's data broker deletion platform goes live

March 26, 2026: Final approval of the Google RTB settlement requiring a control that strips device advertising IDs

May 2026: FTC closes the Kochava case with a consent order

August 13, 2026: Bundeskartellamt accepts Apple's commitments to redesign the ATT prompt

August 31, 2026: ChatGPT ads begin accepting the Google Advertising ID for custom audiences

September 16, 2026: Apple publishes a redesigned ATT prompt for five EU countries

Related PPC Land coverage

Explaining tracking SDK - How third-party SDKs inside apps collect advertising identifiers alongside device and event data.

Explaining bidstream - The fields of an OpenRTB bid request, including the device object that carries the ifa and lmt values.

Explaining mobile measurement partner - How attribution providers matched clicks to installs with device identifiers, and what ATT changed.

Explaining frequency capping - Why caps depend on identifiers, including how Display & Video 360 caps CTV delivery using the IFA.

Apple introduces a compulsory consent manager for all apps with ads - The June 2020 announcement that made IDFA access conditional on user permission.

Google extends Privacy Sandbox initiative to Android, plans to sunset the advertising ID - Google's 2022 plan to replace cross-app identifiers on Android.

Google faces security complaint over real-time bidding data practices - The EPIC and ICCL complaint listing MAIDs among identifiers broadcast in bid requests.

Apple ATT shifted 0.07% of apps to paid downloads, four-year study finds - Reinhold Kesler's study of how app business models and data practices changed after ATT.

Explaining SKAdNetwork - Apple's privacy-preserving install attribution framework that replaced IDFA matching for most iOS traffic.

Explaining pseudonymisation - Why cookie identifiers and mobile advertising IDs remain personal data under European law.

Starlink users can be tracked and identified using ad data, Israeli firms show - How firms say they fused advertising identifiers and bidstream data to deanonymise satellite internet users.

Apple fined 150 million euros: ATT framework ruled anticompetitive - The French competition decision on ATT's double consent design.

Italy fines Apple 98.6 million euros for making developers ask users twice - The Italian competition authority's December 2025 ruling on ATT.

Apple faces four-month deadline to redesign ATT prompt in Germany - The Bundeskartellamt's commitment decision and its findings on Apple's own advertising prompt.

Explaining app bundle ID - How the app identifier in a bid request differs from the device advertising ID.

Explaining cookie syncing - The browser-side process for matching identifiers between companies, absent in apps.

Judge approves Google RTB settlement forcing new user privacy control - The settlement requiring a control that removes device advertising IDs from bid requests.

FTC closes Kochava location data case with strict consent rules - The 2026 order that treats MAIDs combined with location signals as precise location data.

Explaining data broker - How brokers trade identifiers, and how few California deletion requests carried a mobile advertising ID.

OpenAI drops 25,000-user floor for ChatGPT ad exclusion audiences - The August 2026 update adding the Google Advertising ID to ChatGPT audience matching.

5 EU countries lose Apple's standard tracking prompt for a redesigned one - Apple's September 2026 prompt changes and the latest ATT opt-in figures.

Summary

Who. Apple and Google issue the identifiers on iOS and Android, as Roku, Amazon and other television platforms do on CTV. App developers and their SDKs read them; SSPs pass them to DSPs; measurement partners, data brokers and advertisers use them. IAB Tech Lab defines how they travel, and competition and privacy regulators in the US and Europe set the limits.

What. A mobile advertising ID is a random, user-resettable UUID that the operating system exposes to every app on a device for advertising purposes. It travels in the ifa field of OpenRTB bid requests and returns as a string of zeros when a user refuses, deletes or opts out.

When. Apple introduced the IDFA in September 2012 and Google its advertising ID in October 2013, both replacing permanent device identifiers. Apple made access opt-in with ATT on April 26, 2021; Google zeroed the ID for opted-out users from late 2021 and, in October 2025, abandoned the Android Privacy Sandbox APIs meant to replace it.

Where. It operates inside mobile apps on phones and tablets and, through platform equivalents, on connected televisions and streaming devices. It does not exist in web browsers, where cookies fill the same role.

Why. Apps share no cookies, so advertisers need a common value to target, cap frequency and attribute installs across them. The same persistence that makes it useful for advertising lets data brokers and others tie a device's movements to a person, which is why platforms, regulators and courts continue to restrict it.

Luis Rijo

Luís Rijo has written PPC Land daily since founding it in 2016. Over 10,000 articles, funded by readers, no sponsored coverage. Tips and corrections: luis@ppc.land

解读移动广告 ID（MAID） 原文标题：Explaining mobile advertising ID