diff --git a/README.md b/README.md
index 9300bb21..29008223 100644
--- a/README.md
+++ b/README.md
@@ -130,6 +130,23 @@ You can find a lot more about configuring Grist, setting up authentication,
 and running it on a public server in our
 [Self-Managed Grist](https://support.getgrist.com/self-managed/) handbook.
 
+## Activating the boot page for diagnosing problems
+
+You can turn on a special "boot page" to inspect the status of your
+installation. Just visit `/boot` on your Grist server for instructions.
+Since it is useful for the boot page to be available even when authentication
+isn't set up, you can give it a special access key by setting `GRIST_BOOT_KEY`.
+
+```
+docker run -p 8484:8484 -e GRIST_BOOT_KEY=secret -it gristlabs/grist
+```
+
+The boot page should then be available at `/boot/<GRIST_BOOT_KEY>`. We are
+starting to collect probes for common problems there. If you hit a problem that
+isn't covered, it would be great if you could add a probe for it in
+[BootProbes](https://github.com/gristlabs/grist-core/blob/main/app/server/lib/BootProbes.ts).
+Or file an issue so someone else can add it, we're just getting start with this.
+
 ## Building from source
 
 To build Grist from source, follow these steps:
@@ -242,6 +259,7 @@ GRIST_ADAPT_DOMAIN  | set to "true" to support multiple base domains (careful, h
 GRIST_ALLOWED_HOSTS | comma-separated list of permitted domains origin for requests (e.g. my.site,another.com)
 GRIST_APP_ROOT      | directory containing Grist sandbox and assets (specifically the sandbox and static subdirectories).
 GRIST_BACKUP_DELAY_SECS | wait this long after a doc change before making a backup
+GRIST_BOOT_KEY | if set, offer diagnostics at /boot/GRIST_BOOT_KEY
 GRIST_DATA_DIR      | directory in which to store document caches.
 GRIST_DEFAULT_EMAIL | if set, login as this user if no other credentials presented
 GRIST_DEFAULT_PRODUCT  | if set, this controls enabled features and limits of new sites. See names of PRODUCTS in Product.ts.