SAR Viewer Guide

Best Free SAR Imagery Viewers (2026)

Every free SAR viewer shows the same Sentinel-1 data. What separates them is what you have to bring: an account, code, or nothing at all. Compared by job.

Open the Sentinel-1 SAR viewer Compare all imagery tools

Quick answer — what Off-Nadir Delta is

Free SAR imagery means Sentinel-1, and four tools cover most needs. Copernicus Browser is the official viewer and download point, with a free account. ASF Vertex searches SAR scenes across missions and orders processed products such as RTC and InSAR. Google Earth Engine runs large-scale analysis in code on a registered Cloud project. Off-Nadir Delta shows recent Sentinel-1 passes on a live map with no login, next to optical imagery, fire detections and located world events. Pick by whether you need a picture, the data, or an analysis.

Free SAR viewers compared at a glance

Facts last reviewed 2026-10-04.

Tool	SAR data	Shows imagery in the browser	Account	Coding required	Processing
Copernicus Browser	Sentinel-1 (SM, IW, EW), plus Sentinel-2, -3, -5P	Yes	Free account needed	No	Visualizations, compare, timelapse
ASF Vertex	Sentinel-1, NISAR, ALOS PALSAR, OPERA-S1 and more	Browse images	Free Earthdata Login for On Demand and saved searches	No	On Demand RTC and InSAR
Google Earth Engine	Sentinel-1 GRD from Oct 2014	yes, from code	Cloud project registered for Earth Engine	Yes	Anything you script
Off-Nadir Delta	Sentinel-1 (VV, VH); NISAR L-band on paid plans	Yes	No account for the live map; free account for scene search	No	Viewing; ship detection and monitoring metered

Third-party cells are from each provider’s own documentation: the Copernicus Browser documentation, the ASF Vertex manual, and the Google Earth Engine Sentinel-1 catalog entry and access guide. Off-Nadir Delta is an independent project and is not affiliated with any of them.

A picture, the data, or an analysis?

Most people looking for a SAR viewer want one of three things, and each tool is built around one of them. Deciding which you need is faster than trying every tool.

A picture

What does this place look like in radar, through cloud or at night? A browser viewer answers this in a minute.

The data

The scene itself, or a processed product such as RTC or an interferogram, to use in your own software.

An analysis

Statistics or a time series over a large area, which means writing code or using a tool that measures for you.

The best free SAR viewers, by job

Copernicus Browser

Best as the official viewer for Sentinel-1

The Copernicus Data Space Ecosystem Browser, described in its documentation as a central hub for accessing, exploring and utilizing the data of the Copernicus Sentinel constellations. It covers Sentinel-1 in SM, IW and EW modes alongside Sentinel-2, Sentinel-3 and Sentinel-5P, with a latest-date button, a compare mode for two or more visualizations, and a timelapse export.

Best for:: Viewing and downloading Sentinel-1 straight from the official source, with the full archive and the other Sentinel missions in the same place.
Limitation:: Its documentation says a free account is currently needed to use the Browser, and it is a data viewer: it does not tell you where something is happening or why a scene matters.

ASF Vertex

Best for finding and downloading SAR scenes across missions

The Alaska Satellite Facility’s SAR data search. Its manual lists Sentinel-1, NISAR, ALOS PALSAR and OPERA-S1 among the searchable datasets, shows browse images in an image viewer, and links to On Demand processing for products such as RTC and InSAR.

Best for:: Searching the SAR archive by area, date and orbit, and ordering processed products when you need the data itself.
Limitation:: It is a search and download tool: you see browse images rather than a full-resolution map layer, and On Demand processing requires signing in with a free Earthdata Login.

Google Earth Engine

Best for large-scale SAR analysis in code

A cloud analysis platform whose data catalog includes the Sentinel-1 SAR GRD collection from October 2014 onward. The catalog states that scenes are pre-processed with thermal noise removal, radiometric calibration and terrain correction, and converted to decibels.

Best for:: Time series and statistics over large areas, when you can write the analysis yourself.
Limitation:: It is driven by code, and it needs a Google Cloud project registered for noncommercial or commercial use; commercial use requires a paid plan.

Off-Nadir Delta(that’s us)

Best for looking at a place in SAR without an account, then acting on it

A live Sentinel-1 map that runs on the page with no login, stacking the last 6 days of radar passes worldwide. With a free account, search Sentinel-1 scenes over an area and view them at 10 m in VV or VH on the same map as Sentinel-2 optical imagery, NASA FIRMS fire detections and located world events.

Best for:: Checking what a place looks like in radar right now, and tying it to a reported event or a watch on the same site.
Limitation:: It is not a download or processing service: there is no raw scene download and no InSAR, and analysis beyond viewing is metered. For the data itself, go to Copernicus Browser or ASF Vertex.

Frequently Asked Questions

What is the best free SAR viewer?▼

It depends on what you need to do. For the official view and download of Sentinel-1, use Copernicus Browser. To search SAR scenes across missions and order processed products, use ASF Vertex. For large-scale analysis in code, use Google Earth Engine. To look at a place in radar without creating an account, and to tie what you see to a reported event, use the Off-Nadir Delta Sentinel-1 viewer. All four show the same free Sentinel-1 data.

Is Sentinel-1 SAR imagery free?▼

Yes. Copernicus states that Sentinel data products are made available systematically and free of charge to all data users, including the general public, scientific and commercial users. What differs between tools is whether you need an account, whether you need to write code, and whether the tool shows the imagery or only lets you download it.

Can I view SAR imagery without an account?▼

The Off-Nadir Delta Sentinel-1 viewer shows recent Sentinel-1 passes on a live map with no login. The Copernicus Browser documentation says a free account is currently needed to use it. Google Earth Engine needs a registered Cloud project. ASF Vertex requires a free Earthdata Login for On Demand processing and saved searches.

What happened to EO Browser?▼

The EO Browser web interface from Sentinel Hub was retired on 20 March 2026; public-data users were pointed to Copernicus Browser. If you used EO Browser to look at Sentinel-1, Copernicus Browser is the direct successor for the same data.

Why does SAR imagery look so different from a photo?▼

SAR is radar. Sentinel-1 operates at a centre frequency of 5.405 GHz and images day and night regardless of the weather, according to the Copernicus mission documentation. Brightness shows how strongly the surface returns the radar signal, so calm water is dark, and buildings and ships are bright. It does not show colour.

How often does Sentinel-1 image the same place?▼

The Copernicus mission documentation gives a 12-day repeat cycle for a single satellite and a six-day repeat cycle for the two-satellite constellation. To find the date of the next pass over a specific place, use satellite pass prediction.