Add your MOL file
Drop one or more .mol files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
MOL to JSON
Converting a .mol font to .json repackages the same glyphs and metrics for a different delivery target. Free, private, and validated — the file never leaves your browser.
Private for supported formats — processed in your browser
Runs on your deviceConvert supported files
Drop MOL files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting MDL Molfile to JSON data
Converting a .mol font to .json repackages the same glyphs and metrics for a different delivery target. A .mol file is an MDL Molfile: a chemical structure written as a connection table — a counts line, then one fixed-width line per atom giving its coordinates and element, then one line per bond giving the two atoms it joins and its order. It describes a molecule's topology, not its appearance.
A .json file holds JavaScript Object Notation: nested objects, arrays, strings, numbers, booleans, and null written in a strict text syntax. It is the default data language of the web — most APIs speak nothing else. For this route the practical draw is parsers ship in the standard library of essentially every language and readable by humans and machines alike — balanced against no comments — a perpetual annoyance for configuration files, which is worth knowing before you commit a large batch.
Why convert MOL to JSON?
The practical trigger for this conversion is usually a mismatch: with .mol, v2000's 999-atom limit rules out proteins and large systems. Switching to .json buys you parsers ship in the standard library of essentially every language, which is why it is the better fit for rEST and HTTP API request and response payloads. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
MOL vs JSON at a glance
| Aspect | MDL Molfile (.mol) | JSON data (.json) |
|---|---|---|
| Format type | Text-based — characters and structure, so there is no visual quality loss | Text-based — characters and structure, so there is no visual quality loss |
| How it stores data | the first three lines are a title, a program/timestamp line and a comment, before any structural data | exactly six value types; no dates, no comments, no trailing commas — the strictness is deliberate |
| Strongest at | exchanging a single molecular structure between chemistry applications | rEST and HTTP API request and response payloads |
| Weak spot | v2000's 999-atom limit rules out proteins and large systems | no comments — a perpetual annoyance for configuration files |
Pick JSON as the output
Select .json in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if JSON is selectable, the route is real and validated.
Convert on your device
Press Convert. The font tables are parsed and rewritten locally with fonteditor-core; glyph outlines, hinting, and kerning survive the trip.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid JSON file. Outputs keep the original filename with the .json extension.
MOL to JSON questions, answered
Will converting MOL to JSON lose quality?
There is no visual quality to lose — mol is text-oriented and json is text-oriented, so the question is structural fidelity. Text, ordering, and basic structure are preserved; complex layout, embedded objects, and styling beyond the target's model are simplified.
Is it private to convert MOL files here?
Yes — the .mol file is processed inside your browser tab and never uploaded. The font tables are parsed and rewritten locally with fonteditor-core; glyph outlines, hinting, and kerning survive the trip. Close the tab and the file is gone from memory.
Where will the JSON file work?
Browsers parse it natively through JSON.parse, every mainstream language bundles support, and most editors validate and highlight it out of the box. Viewing a raw .json file is possible in any text editor or browser tab.
Will the JSON file be bigger or smaller than my MOL?
It depends on the content: exactly six value types; no dates, no comments, no trailing commas — the strictness is deliberate. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my MOL file?
In .mol, atom coordinates, element symbols, bond orders and the title line are preserved. Property blocks after the connection table are not carried into every target. Re-encoding through the browser pipeline does not carry embedded metadata into the output, which doubles as a privacy scrub — check the exported file if you specifically need tags preserved.