LinkedIn ID Decoder

A single-file browser tool that extracts exact timestamps from LinkedIn post, comment, and reply URLs.

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How This Started

This started with a simple question: when exactly did I write that? I had a LinkedIn post from a while back and wanted to know the precise date. The timestamp LinkedIn displays is vague at best and disappears into "a while ago" territory fairly quickly. So I went digging.

It turns out that LinkedIn, like many large platforms, uses a Snowflake ID system. Every post, comment, and reply is assigned a 19-digit ID that has the creation timestamp baked directly into it. Once you know how to decode it, the exact date and time is sitting right there in the URL, down to the millisecond.

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What It Does

Paste a LinkedIn URL and the tool will extract and display:

• The exact date and time the original post was created
• The exact date and time of a comment, if the URL points to one
• The exact date and time of a reply to a comment, if present
• The time gap between post and comment, or between comment and reply

All times are shown in your chosen timezone as well as UTC.

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How the Decoding Works

LinkedIn Snowflake IDs are 64-bit integers. The first 42 bits encode the timestamp in milliseconds. To extract it, the tool performs a bitwise right shift of 22 positions, which strips away the internal machine and sequence bits and leaves the millisecond timestamp. That is then converted into a standard JavaScript Date object.

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How to Use It

This is a single HTML file with no dependencies, no build step, and no server required.

Running It

Download linkedin-id-decoder.html and open it in any modern browser. That is it.

git clone https://github.com/rilhia/linkedin-id-decoder.git
cd linkedin-id-decoder
open linkedin-id-decoder.html

Or simply double-click the file.

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Getting the Right URL

The URL you need is not always the one in your browser's address bar. To get the correct link:

For a post: Navigate to the post and copy the URL from the address bar. It should contain a 19-digit number.

For a comment: Click the three-dot menu on the comment and select Copy link to comment. This gives you a URL containing the comment ID.

For a reply to a comment: Click the three-dot menu on the reply itself and select Copy link to comment. This gives you a URL containing both the comment ID and the reply ID.

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Using the Tool

1. Open the tool in your browser
2. Paste your LinkedIn URL into the input field
3. Select your preferred timezone from the dropdown (defaults to your local timezone automatically)
4. The results appear instantly

The tool handles both standard LinkedIn URL formats and the newer dashCommentUrn / dashReplyUrn format automatically.

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What the Results Show

Section	Colour	What It Means
Original Post	Blue	When the post was first published
Comment	Green	When the comment was posted
Reply to Comment	Red	When the reply was posted
Time Gap Indicator	Blue banner	Seconds elapsed between each event

Each result also shows the raw epoch timestamp in milliseconds, which is useful if you want to do further calculations.

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Supported URL Formats

The tool handles the following LinkedIn URL patterns:

• /feed/update/urn:li:ugcPost:XXXXXXX
• /feed/update/urn:li:activity:XXXXXXX
• URLs containing commentUrn or dashCommentUrn parameters
• URLs containing replyUrn or dashReplyUrn parameters

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Privacy

Everything runs entirely in your browser. No data is sent anywhere. No analytics. No tracking. The tool never sees your LinkedIn credentials or session.

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Limitations

• The tool requires a URL that contains a Snowflake ID. Shortened or redirected URLs may not work until they resolve to a full LinkedIn URL.
• LinkedIn occasionally changes its URL structure. If a URL is not being decoded, check that it contains a 19-digit numeric ID.

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Licence

MIT. Use it, modify it, share it freely.

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Built by Richard Hall