diff --git a/src/atom.cpp b/src/atom.cpp
index 2678326338..8b04accc13 100644
--- a/src/atom.cpp
+++ b/src/atom.cpp
@@ -2124,7 +2124,7 @@ int Atom::shape_consistency(int itype, double &shapex, double &shapey, double &s
 }
 
 /* ----------------------------------------------------------------------
-   add a new molecule template = set of molecules
+   add a new molecule template = set of molecules from the "molecule" command
 ------------------------------------------------------------------------- */
 
 void Atom::add_molecule(int narg, char **arg)
@@ -2153,6 +2153,25 @@ void Atom::add_molecule(int narg, char **arg)
   }
 }
 
+/* ----------------------------------------------------------------------
+   add a new molecule template from a JSON object
+------------------------------------------------------------------------- */
+
+void Atom::add_molecule(const std::string &id, const json &moldata)
+{
+  if (id.empty()) error->all(FLERR, "Must provide molecule ID");
+
+  if (find_molecule(id.c_str()) >= 0)
+    error->all(FLERR, Error::NOLASTLINE, "Reuse of molecule template ID {}", id);
+
+  molecules = (Molecule **)
+    memory->srealloc(molecules,(nmolecule+1)*sizeof(Molecule *), "atom::molecules");
+  molecules[nmolecule] = new Molecule(lmp);
+  molecules[nmolecule]->from_json(id, moldata);
+  molecules[nmolecule]->nset = 1;
+  nmolecule++;
+}
+
 /* ----------------------------------------------------------------------
    find first molecule in set with template ID
    return -1 if does not exist
diff --git a/src/atom.h b/src/atom.h
index c98f06cbe8..86d81c0148 100644
--- a/src/atom.h
+++ b/src/atom.h
@@ -16,6 +16,8 @@
 
 #include "pointers.h"
 
+#include "json.h"
+
 #include <map>
 #include <set>
 
@@ -358,6 +360,7 @@ class Atom : protected Pointers {
   int shape_consistency(int, double &, double &, double &);
 
   void add_molecule(int, char **);
+  void add_molecule(const std::string &, const json &);
   int find_molecule(const char *);
   std::vector<Molecule *> get_molecule_by_id(const std::string &);
   void add_molecule_atom(Molecule *, int, int, tagint);
diff --git a/src/molecule.cpp b/src/molecule.cpp
index cb6562612e..3b9502c698 100644
--- a/src/molecule.cpp
+++ b/src/molecule.cpp
@@ -27,6 +27,7 @@
 #include "math_special.h"
 #include "memory.h"
 #include "tokenizer.h"
+#include "update.h"
 
 #include <cmath>
 #include <cstring>
@@ -184,10 +185,10 @@ void Molecule::command(int narg, char **arg, int &index)
     // convert back to json class on all processors
     moldata.clear();
     moldata = json::from_ubjson(jsondata);
-    jsondata.clear(); // free binary data
+    jsondata.clear();    // free binary data
 
     // process JSON data
-    Molecule::from_json(moldata);
+    Molecule::from_json(id, moldata);
 
   } else {    // process native molecule file
 
@@ -209,9 +210,15 @@ void Molecule::command(int narg, char **arg, int &index)
 //  convert json data structure to molecule data structure
 // ------------------------------------------------------------------------------
 
-void Molecule::from_json(const json &moldata)
+void Molecule::from_json(const std::string &molid, const json &moldata)
 {
   json_format = 1;
+  if (!utils::is_id(molid))
+    error->all(FLERR, Error::NOLASTLINE,
+               "Molecule template ID {} must have only alphanumeric or underscore characters",
+               molid);
+  delete[] id;
+  id = utils::strdup(molid);
 
   // check if JSON file is compatible
 
@@ -229,7 +236,13 @@ void Molecule::from_json(const json &moldata)
   if (moldata.contains("revision")) {
     int rev = moldata["revision"];
     if ((rev < 1) || (rev > 1))
-      error->one(FLERR, Error::NOLASTLINE, "JSON molecule data with unsupported revision {}", rev);
+      error->all(FLERR, Error::NOLASTLINE, "JSON molecule data with unsupported revision {}", rev);
+  }
+
+  if (moldata.contains("units")) {
+    if (std::string(moldata["units"]) != update->unit_style)
+      error->all(FLERR, Error::NOLASTLINE, "JSON molecule data units {} incompatible with {} units",
+                 std::string(moldata["units"]), update->unit_style);
   }
   if (moldata.contains("title")) title = moldata["title"];
 
diff --git a/src/molecule.h b/src/molecule.h
index 2a9844ddeb..7444342357 100644
--- a/src/molecule.h
+++ b/src/molecule.h
@@ -128,7 +128,7 @@ class Molecule : protected Pointers {
   ~Molecule() override;
 
   void command(int, char **, int &);
-  void from_json(const json &);
+  void from_json(const std::string &id, const json &);
 
   void compute_center();
   void compute_mass();