If you are searching for the softest 3D printing filament, you are usually not choosing between PLA, PETG, and ABS. You are choosing between TPU grades, hardness ratings, and how much print difficulty you are willing to accept to get a more flexible part. That distinction matters, because the softest option on paper is not always the best option on your printer.
For most buyers, the answer starts with TPU. It is the standard flexible material for FDM printing, and it is available in a range of Shore hardness levels. The lower the Shore number, the softer and more rubber-like the filament feels. In practical terms, a TPU rated around 95A is flexible but still manageable on many consumer printers. Drop down into the 90A range and below, and the material becomes noticeably softer, but feeding and control get harder.
What is the softest 3D printing filament?
In standard desktop FDM printing, the softest 3D printing filament is usually a low-Shore TPU or TPE. These are the materials used when a printed part needs to bend, compress, grip, or absorb impact instead of staying rigid.
That said, "softest" needs context. Some sellers use TPU as a broad category even when the material behaves quite differently from one spool to another. A 95A TPU can feel fairly firm in a thick print, while an 85A or softer formulation can feel much closer to rubber. Wall thickness, infill, and geometry also change the final feel of the part. A soft filament printed with thick walls can feel stiffer than a slightly harder filament printed with thinner sections.
For buyers trying to match a use case, Shore hardness is the spec worth watching first. If your goal is phone cases, protective bumpers, gaskets, flexible straps, or vibration-damping parts, TPU is the default choice because it balances softness with real printability.
TPU vs TPE: which one is actually softer?
TPE is often softer in the broad sense, but it is also less common in mainstream desktop printing because it can be harder to feed consistently. TPU is a type of thermoplastic elastomer, but in the 3D printing market, TPU is usually the more practical and widely stocked option.
If you want the softest possible material and you are comfortable tuning your setup, a very soft TPE may outperform standard TPU on flexibility. If you want a material that still has a good chance of printing reliably on hobbyist and prosumer machines, TPU is usually the safer buy. That is why most people asking about softness are really asking which TPU hardness to choose.
For a lot of printers, especially Bowden setups, there is a point where extra softness stops being useful because the filament becomes difficult to push without buckling. Direct drive systems generally handle softer flexible filaments better, but even then, ultra-soft grades slow production and increase failed print risk.
How Shore hardness affects soft filament choices
Shore hardness is the quickest way to compare flexible filaments, but it only helps if you know what the numbers mean in practice. Most flexible 3D printing filaments use the Shore A scale. Lower numbers mean softer material.
A 98A or 95A TPU is often the starting point for users who want flexibility without making the printer fight them. It still bends easily, works for cases and protective parts, and tends to feed more predictably. Around 90A, parts become softer and more compressible. Below that, you are moving into specialty territory where the printed feel may be excellent, but the machine demands go up.
This is where buying decisions get more practical than theoretical. If your printer is not already well-tuned for flexible materials, going for the absolute softest spool available can cost more time than it saves. A slightly firmer TPU often produces better real-world results because the print actually finishes, dimensionally holds, and repeats.
When the softest filament is the wrong choice
There is a common mistake with flexible materials: assuming softer always means better. It does not.
If the part needs to keep its shape under load, a very soft filament may fold too easily. If the print has narrow paths, retractions, or small unsupported features, ultra-soft material may string heavily or deform during printing. If the part needs abrasion resistance and a controlled amount of flex, a mid-range TPU can outperform a softer option because it is more stable.
For example, a cable strain relief, tool grip, or wearable clip often works better in 95A TPU than in a much softer grade. The part still flexes, but it is easier to install, easier to print, and less likely to feel floppy. On the other hand, seals, pads, and compression-based parts can benefit from softer material if the printer can handle it.
So the better question is not just "what is the softest 3D printing filament" but "how soft does this part actually need to be?" That is the question that prevents overbuying specialty filament that does not fit the job.
Printing the softest 3D printing filament without frustration
Flexible filament rewards slower, cleaner printing. Even the best material will print poorly if the feed path has too much open space, the retraction settings are aggressive, or the print speed is closer to PLA than TPU.
Most users get better results by slowing down significantly, reducing retraction, and keeping the filament path constrained. Direct drive extruders usually help because they reduce the distance between drive gears and hotend. Bowden printers can still print TPU, especially firmer grades, but they are generally less forgiving as softness increases.
Moisture control matters too. Flexible materials can absorb water from the air, which leads to stringing, surface defects, and inconsistent extrusion. A dry spool prints more cleanly and gives you a fairer read on what the filament can actually do. If you are comparing brands or hardness levels, dryness needs to be controlled or the comparison is not meaningful.
Bed adhesion is usually manageable, but over-adhesion can be an issue on some surfaces. You want the part to stick during printing without becoming difficult to remove. Like most specialty materials, TPU benefits from testing with a small part before committing to a long run.
What buyers should look for besides softness
Softness gets the headline, but it should not be the only buying factor. Consistency from spool to spool matters more than many people expect. Flexible filament that varies in diameter, winding quality, or moisture content will create feed problems fast.
Brand support and material transparency also matter. A clear hardness rating is useful. So is realistic guidance on print temperature and speed. If a filament is marketed as extremely soft but does not clearly state Shore hardness or printer compatibility, that is a warning sign.
Stock availability matters as well, especially for repeat jobs or small-batch production. If you test one spool and then cannot get the same material again, you lose time requalifying another option. For businesses, schools, and makers running repeatable projects, dependable access often matters more than chasing the softest spec on the market.
This is where a specialized supplier is more useful than a generic marketplace listing. If you are buying TPU for real use, not just experimentation, it helps to source from a seller that already works across flexible, standard, and specialty filament categories and can keep material selection practical. KJI 3D fits that model by focusing on actual material categories, known brands, and straightforward fulfillment.
Best use cases for soft filament
Soft filament makes sense when the part needs grip, impact absorption, compression, or repeated bending. That includes phone cases, feet and pads, protective covers, grommets, straps, living-hinge style components, and some medical or ergonomic prototypes where a rigid plastic would not behave correctly.
It is less ideal for structural brackets, precision snap fits that need stiffness, or decorative prints where speed and surface finish matter more than flexibility. In those cases, softer material adds complexity without solving a real problem.
The practical buying move is to match the hardness to the function, not to the marketing. If you need reliable flexibility, start with a well-reviewed TPU around 95A. If the part truly needs more compression or a more rubber-like feel, step softer from there and confirm your printer can manage it.
The softest filament is only the right filament when the part, printer, and workflow can all support it. Buy for the application first, and the material choice gets a lot easier.