What Is CDR Mapping? A Plain English Guide for 2026
Short version. CDR mapping is the forensic practice of taking a wireless carrier’s call detail records and cell site location information and plotting them on a map. It shows roughly where a phone was, who it talked to, and when. It does not show a GPS point and it does not prove who was holding the phone.
The two pieces: CDR and CSLI
CDR (call detail records) are metadata about calls and texts: the numbers, timestamps, durations, and the originating cell sector. CSLI (cell site location information) is the running list of towers and sectors a phone connected to over time. Plot CDR plus CSLI on a map, and you have a CDR map.
What a CDR map can actually show
- The general area a phone was in at a specific moment (sector level, not GPS).
- The contact pattern between two or more phones across a window of time.
- When a phone was online, offline, roaming, or out of coverage.
- Whether a phone’s recorded movements are consistent or inconsistent with an alleged route.
What it cannot show
- A precise GPS location. Sectors cover hundreds of meters to several miles.
- The contents of any call or text.
- Who was physically holding the device.
- Whether the phone was sitting still or moving inside the sector.
How to preserve the data before it disappears
Cell tower records evaporate fast. Some carriers keep historical CSLI for only about a year, and text content is usually gone in days. The single most important step is sending an 18 U.S.C. 2703(f) preservation request to the carrier the moment a matter becomes likely. That freezes the relevant records for 90 days while the lawful process catches up.
Carrier retention at a glance
- AT&T: CDR roughly 7 years. Text content not retained.
- Verizon: CDR roughly 1 to 7 years. CSLI about 1 year. Text content roughly 3 to 5 days.
- T Mobile: CDR roughly 2 years. Text content generally not retained after delivery.
These windows change. Confirm before relying on them in a real matter.
The legal posture in 2026
Under Carpenter v. United States, 585 U.S. 296 (2018), the government generally needs a warrant for 7 or more days of historical CSLI. Basic subscriber data and call detail records can usually be obtained with a 2703(d) order. Self authentication of carrier records typically runs through Federal Rule of Evidence 902(11).
Need a CDR map for an active matter?
We will tell you what is recoverable, what to preserve immediately, and what a defensible map will and will not say.
Read the full CDR Mapping service pageHow it fits with device forensics
CDR mapping is most powerful when paired with the phone itself. The carrier picture answers where and who. The device picture answers what was said, what was opened, and what was deleted. In contested matters, both are usually needed. See our companion explainer: Cell Phone Forensics vs Cell Tower Records.
Bottom line
CDR mapping is a powerful timeline tool when it is scoped honestly. It can corroborate or rule out a phone’s presence in a geographic area and reveal the contact pattern around an incident. It is not a GPS tracker and it does not identify the user. Treat any expert who claims otherwise with caution.
