ads.txt is a plain-text file stored at the root of a publisher's domain that lists which companies are authorized to sell the site's advertising inventory, and an ads.txt generator on Android is the fastest way to build that file from a phone using only the mobile browser. A standards-shaped record contains exactly three required comma-separated fields per line — the advertising system domain, the publisher account identifier, and a DIRECT or RESELLER relationship — followed by an optional fourth field for a certification authority identifier supplied by an external auditor such as the Trustworthy Accountability Group. Because the deliverable is plain text, Android users do not need to install a dedicated app; the same content can be produced in Chrome, Samsung Internet, or any mobile browser and the finished file can be saved with the device's normal download flow, then opened in a text editor or pushed straight to the site root.
What an ads.txt File Actually Does
Publishers running programmatic ads depend on ads.txt to make their inventory crawlable and verifiable. The file sits at a single canonical location — example.com/ads.txt — and buyers cross-check every seller record against the publisher's own declaration before spending money, which lowers the risk that counterfeit inventory is resold under the site's name. The format was published by the IAB Tech Lab as Ads.txt 1.1 and continues to be updated through industry feedback. It is not an app, a CMS plugin, or a config dashboard; it is just plain text with one record per line, and a buyer-side crawler reads it as it would read any other file on the web.
The IAB specification, available as the public Ads.txt 1.1 PDF, defines three required fields and one optional field per record. The first field is the canonical advertising system domain where programmatic buyers connect. The second field is the seller or publisher account ID that the advertising system assigned. The third field declares the relationship as either DIRECT or RESELLER. The fourth field is optional and is used only when an advertising platform publishes a certification authority identifier, such as the TAG-validated example from Google's documentation.
The Fields an ads.txt Record Requires
| Position | Field | Required? | Example value | Notes |
|---|---|---|---|---|
| 1 | Advertising system domain | Yes | google.com | Bare lowercase domain. No https://, no path, no port, no credentials. |
| 2 | Publisher account ID | Yes | pub-0000000000000000 | Format depends on the platform; copy the literal value from the platform's own instructions. |
| 3 | Relationship | Yes | DIRECT | Use DIRECT when you control the account, RESELLER when another entity controls it. |
| 4 | Certification authority ID | No | f08c47fec0942fa0 | Leave blank unless the platform explicitly supplies a value for that seller record. |
The third field is the most commonly mistaken. DIRECT means the publisher directly controls the account in the seller record and has a direct contract with the advertising system. RESELLER means another entity — typically an SSP, network, or third-party partner — controls the listed account and is allowed to resell the inventory. Selecting the wrong relationship makes the declaration inaccurate even when every character is formatted correctly, so verify this with each partner rather than guessing.
The fourth field also trips up publishers moving between platforms. Google's published guidance uses f08c47fec0942fa0 as the TAG certification identifier for Google AdSense seller records, but that value does not apply to every exchange. Only fill the field in when the advertising platform supplies the exact identifier for the record being added; otherwise leave the column blank, which is what the spec expects. For a quick reference on field shapes and output formatting, the ads.txt field rules cheat sheet walks through the same rules with extra sample rows.
How to Build ads.txt on an Android Phone
Android does not need a dedicated app for this task. The Ads Txt Generator works in any mobile browser, including Chrome on Android, and the finished file behaves like any other download. The whole workflow fits inside a single phone session and the resulting file is plain text, so it does not need special viewers or converters to be checked or edited later.
- Open the browser on your Android device and navigate to the Ads Txt Generator. The page renders the input form without any installation or sign-in step, which keeps the credentials you are about to paste inside your own device.
- Pull up the advertising platform's setup page — for most Android workflows that is Google AdSense, Google Ad Manager, or another SSP dashboard — and copy the four pieces of information it provides: the canonical advertising system domain, the publisher account ID, the relationship (DIRECT or RESELLER), and any certification authority ID that the platform publishes for that record.
- Type the first field as a bare domain such as google.com, exactly as it appears in the platform's instructions. Do not add https://, do not add a path like /ads.txt, do not include a port, username, or password. The generator lowercases the domain and validates it instead of silently extracting a host from a pasted URL, so on-screen typing-mistake messages surface immediately.
- Enter the publisher account ID exactly as the platform provides it. For Google seller accounts the official format begins with a pub- prefix followed by digits. Other exchanges use different identifiers, so copy the literal value from the platform's own instructions rather than inventing or converting one yourself.
- Pick DIRECT if you control the account and contract directly with the advertising system, or RESELLER if another entity controls that account and is authorized to resell your inventory. The selector only accepts those two values.
- Leave the certification authority field empty unless the platform's documentation supplies an exact identifier for that record. Google's example value is f08c47fec0942fa0. Do not paste that number into records from other exchanges.
- Tap the button to add the seller to the visible list. Repeat for every authorized seller. The generator prevents exact duplicate rows, trims stray whitespace from each field, and rejects commas or whitespace inside fields, so a sloppy paste cannot poison the output.
- Review the full list of generated lines on screen. On a phone screen this often means scrolling slowly — read every record top to bottom and remove any seller that is no longer authorized or that overlaps a duplicate entry.
- Tap the download control to save the file. Android will place the file in the Downloads folder with the name ads.txt, which matches what the spec requires. You can also copy the text to the clipboard if you want to paste it into a CMS text field instead.
- Upload the file to the root of the domain that owns the inventory. For example, the expected public location for example.com is https://example.com/ads.txt. Hosting it only under /files/ads.txt, embedding it inside an HTML page, or placing it behind authentication does not create the same crawler-visible root resource, so the declaration will not take effect.
- Open https://yourdomain.com/ads.txt in the same Android browser after deployment and read the result as plain text. Compare each line against the original platform instructions to confirm that the deployment matches what you generated.
Browser-only tools deliberately do not call the network. Account identifiers are never sent to a server, which matters when a publisher is signing into back-office dashboards on the same device and does not want their IDs leaking through third-party log endpoints.
Limits the Tool Enforces for You
Mobile pasting on a phone keyboard is prone to junk characters, so the generator ships with several guard rails rather than silently producing broken output. Each seller row is parsed as three required comma-free tokens plus one optional token. Surrounding input is trimmed. Internal commas and whitespace inside any field are rejected. Domains are normalized to bare lowercase DNS-style hosts, so pasting Google.com produces google.com. Exact duplicate rows are blocked. The output always ends with a single newline terminator, which keeps the file well-behaved for crawlers that expect a trailing newline.
The generator supports up to 200 records so that a mistaken oversized paste cannot produce an unwieldy browser result. If you exceed that ceiling, the right-sized next step is usually to split records across multiple files — for example, separate web ads.txt for the main site and app-ads.txt for app inventory — rather than to keep piling rows into one file. The page validates syntax. It does not validate authorization. A record can be syntactically perfect and still be a seller you never approved, so the platform-side review step stays in your hands.
Where to Upload ads.txt and How to Verify It
Deployment is where most mobile workflows fall down. A valid ads.txt file has to live on the root of the domain that owns the advertising inventory, not inside a subdirectory, a CDN path, or an HTML container. If your site is example.com, the crawlers look at https://example.com/ads.txt and nowhere else. Subdomains and second-level domains each need their own file when their inventories are different.
Keep a backup of the prior file before changing anything, then diff the new content against the backup so any removal is intentional. Do not delete existing valid sellers merely to add a new one. After deployment, open the public URL in your Android browser and view it as plain text. Some CMS themes route the file through a parser that adds wrapper HTML, which breaks crawler discovery — in that case serve the file directly from the web root rather than from the templating layer.
If you change ad networks later, edit the file again with the same workflow. Add the new seller, leave the verified existing entries untouched, and re-upload. Account or partnership changes may require future updates, and there is no automation that can write that file for you safely, since the spec intentionally treats the human review as part of the security model.
For a deeper look, see Common Mistakes That Skew an AI Bot Robots.txt Check.